A yinrih womb nest, a highly derived egg-sac with its own simple heart and circulatory system. A central bus artery feeds oxygenated blood to the kits, and returning veins pass through a semi-permeable dermal layer to allow for gas exchange. The arrangement of kits in the womb nest is what gives womb ships their name, as suspension capsules are arranged in a similar manner.
In early yinrih history, as well as among the yinrih's nonsapient congeners, the tree dwellers, womb nests are placed in a dry place that can be easily defended from predation by oviraptors and infanticide from rival conspecifics. In modern times, however, a womb nest incubator is used.
A womb nest incubator consists of an inner capsule into which the male and female eggs are placed. The capsule is transparent to allow visual inspection of the nest's exterior. The capsule sits atop a suspension system to cushion the womb nest against sudden movements. The capsule and suspension are encased in a ruggedized outer chassis that also contains a number of other components.
Chief among these is a redundant power supply, accepting both external power and a backup power source, likely a star lantern. There is a two-step air filtration system. The first step processes air going from the environment to the chassis interior, and the second step filters this air in turn before venting it into the inner capsule. Waste gases exchanged by the nest's vascularized dermis are expelled into the chassis and subject to monitoring by the incubator. Medicine and vaccines are typically delivered via aerosol through the ventilation system.
When the dermis is fully developed, a cannula is connected from the nest's interior cavity to a port on the inner capsule. This allows exploratory inspection and prenatal surgery by a healer piloting a micro mech. There is traditionally one such inspection shortly before the kits are yeaned, and it is here where in many cultures kits receive their names. At this point their coats are developed, and they are near or at their birth weight. Names are often given based on their behavior in utero during this inspection. Some may be more alert than others, responding to the pill-sized mote of light outside their amniotic sac by turning their head or reaching out with a paw[^1]. Kits that respond this way are traditionally thought to be destined for holiness.
In addition to the expected systems monitoring the vital signs of the developing kits and the womb nest itself, there are environmental sensors to detect ambient temperature and air pressure. If the ambient pressure drops suddenly, for example due to a hull breach on an orbital colony, the exterior ventilation will be sealed and the air supplied to the inner capsule will divert to an on-board emergency supply.
The outer chassis is famously sturdy. It is shielded against radiation and hard vacuum (again to accommodate spacers) and can withstand the crushing pressures of the deep ocean (to accommodate Sweetwater's benthic cities.) It can even withstand small arms fire.
The reason why incubators are built to withstand everything short of quasiluminal munitions has to do with paternal instinct. The incubator is usually kept in the home and monitored remotely by a healer. During the kits' gestation, the sires are compelled by instinct to protect their nest, to the point of forgetting to eat. Their only waking thought is "THESE ARE THE ONLY CHILDREN I WILL EVER HAVE; I MUST PROTECT MY BABIES!"
Sires will respond aggressively to other males approaching their nest, which is one of the reasons why the medical profession is dominated by women. Women who are not part of the childermoot can examine the nest without getting eviscerated at the claws of up to six overprotective fathers. This aggression is at its height when a sire is in close proximity to his nest, but he will remain more or less irascible throughout his kits' gestation, to the point that paternity leave is legally mandated in most jurisdictions.
Since yinrih only have one litter in their lifetime, incubators are rarely purchased outright. Small communities such as a lighthouse or other house of worship may have incubators that they loan to expecting childermoots, or they may be rented or loaned by a healthcare organization, private company, or government entity.
The inner capsule is discarded after use, and the chassis is cleaned and inspected between uses.
After yeaning, the empty womb nest may be disposed of, or the stem cells or blood within may be harvested in case of future need by one or more of the pups. In certain atavist communities the nest is eaten by the childermoot or just the sires (who haven't been eating properly the last five months), mimicking a behavior seen in tree dwellers.
After the kits are yeaned the incubator is returned.
Gestation lasts about 144 days from the time the eggs are gathered together. Yeaning is the proper term for when kits emerge from the womb nest. Humans often call it "hatching", and some yinrih go along with it when synthesizing English. Yeaning is initiated when the womb-nest’s heart stops pumping. This isn't immediately sensed by the kits as their own hearts pick up some of the slack, but the increased load on their hearts tells them it's time to go. This doesn't happen to all the kits simultaneously. The largest or most active kit is usually the initiator. Using their claws they pierce their amniotic sac and then the outer dermis of the womb-nest itself. If they weren't moved to act by the heart stopping, the massive increase in light pouring in through the rent in the dermis made by the first little trailblazer is usually enough stimulation to get the others stirring.
Not all litters have an obvious runt, but most large ones will. The runt is often the last to emerge, hence why the Commonthroat word for runt literally means "little last one". They frequently need a bit of help from one of their dads. Whether and to what extent this help is given is subject to much debate in the medical community and superstitions and traditions abound. On one end of the spectrum, some say that a sire should completely remove the runt from his or her amniotic sac manually. On the other end, some say that fighting their own way out helps build the runt's weak musculature, stimulates their less robust heart and lungs to work harder, or it just builds character. Many split the difference and pierce the amniotic sac and let the kit do the rest. Which sire gets to do this is also subject to cultural particulars. Some say the youngest sire should do it, others the oldest, still others say that if one of the sires was himself a runt he should do it.
Among Sweetwater's surface dwellers, it's a common superstition that the runt (or any kit that dawdles in their amniotic sac and needs to be coaxed out) has an affinity for water and will make a good sailor. Around Moonlitter, this same phenomenon is interpreted as the kit being destined for interstellar mission work.
Smaller yinrih, often runts, are prized for their ability to negotiate tight passages. This is most relevant to the Farspeakers and their secular inheritors.
Meanwhile, the first kit to emerge has their own cultural associations. Some say they have a strong desire to witness Creation and are destined to become research monks. If they are female, it is said by some that their desire to bask in the light shows they will one day become a hearthkeeper. If male, their vigor and strength will push them to a career in law enforcement or the military, or in more pious enclaves, to the Knights of the Sun.
The sires are traditionally the first to handle the kits, the culmination of months of diligence and protection. After toweling them off, they'll get passed around from dad to dad, getting a quick nuzzle and sniff before being handed off to the moms to be nursed for the first time. First Nursing is also steeped in tradition. The sires usually eat a huge meal and then go into torpor, both of which were in short supply during the kits' gestation.
The dams get to bond with their kits as they nurse for the first time. When nursing, the dam will lie on her back with one or two kits resting on her belly. She will cup the kit's head in her forepaw, and the kit will start licking her lactation patch. Saliva stimulates lactation. This can be the dam's or the kit's. If the kit proves particularly fussy the dam will initiate lactation by licking her paw herself. The scent of the milk is usually enough to get the kit to start licking.
As mentioned several times before, adult yinrih don't tolerate physical contact, but kits and younger pups often receive affection from their sires and dams. During nursing a dam will often stroke the kit's head and back with her thumb. This aids digestion. Just like humans, kits will sometimes spit up.
The image of a dam cradling a nursing kit's head in her paw is the quintessential symbol of motherhood cross-culturally, and has given rise to the mild oath "By the palms that nursed me!" or just "palms!"
[^1]: This is a tentative retcon, as I previously said the kits are born blind.
I'm already running a proxmox server on an old laptop. Maybe I could look into that. I need to figure out USB passthrough for the zwave and zigbee dongles.