Nutrition in the advanced embryos of the scorpion:Palamnaeus scaber Thorell

Summary

A highly specialised embryonal nutritional apparatus seen in the embryos ofPalamnœus scaber Thorell. is described. The eggs are yolkless and their entire development takes place in diverticula of the maternal ovarian tubes. During development each embryo enlarges enormously in bulk and so naturally has to be richly nourished. For this purpose the distal end of the diverticulum is drawn out into an “appendix” which forms an absorbing organ and lies free in the hæmolymph from which nutrient materials are taken up. The middle portion of the appendix appears to serve as a reservoir while its proximal end is a hollow chitinised tube— —‘the teat” —inserted into the mouth of the embryo. The absorbed nutrient fluids pass into the gut of the embryo through this “teat”. This mechanism thus suggests the arrangement of a “feeding-bottle”.

Some leading types of relationship between viviparous animals and their embryos are recounted to show that there is nothing parallel to this mechanism in any of the well-known examples. At birth the embryos alone come out, the diverticula with the feeding mechanisms being retained in the maternal hæmocoele, where they rapidly undergo degeneration as new diverticula develop.