214 



»Endoderm«. This is the same as the »ovary y« of figure 28 of my ori- 

 ginal paper, and as Kowalevsky's »Eierstocksrohr«. 



In a transverse section at the base of a very young Salpa it has the 

 general appearance which is shown in S a - 

 1 en sky's figures 3, 4 and 7 (Knospung 

 derSalpen), but careful examination of very 

 thin sections of my perfectly preserved spe- 

 cimens showed that the minute details of 

 his account are far from correct, probably 

 because his specimens were not perfectly 

 preserved , or perhaps because they were 

 not sufficiently hardened to furnish very 

 thin sections. He figures the organ as made 

 up of a compact mass of cells, which are in 

 contact with each other, but careful exami- 

 nation shows that the central portion of the 



Fig. 1. Tansverse section of the organ consists of a granular ground sub- 

 proximal end of a very younar ^ • i • i i . ^ n ti 

 stolon, a Ectoderm, h Nerve Stance, m which oval, transparent cell-like 



tube, c, (7 upper and lower blood- bodies are scattered, at some distance from 

 tubes, J central tube, Salens- i -i a i • v. mi i, ii, i. 



ky's Athemrohr, and Kowa- e^^h other. A high power will show that 



levsky's Darmrohr, h Ovary, each of these bodies is a germinative ve- 

 Salensky's Endoderm, ^^ Sa- • i -.i 4. ^ ^ a ^^. -t. 



le n sky's Mesoderm, Kowa- sicle, with a central nucleus, suspended to its 



levsky's Cloakalröhre. Avail by a reticulum of five radiating proto- 

 plasmic threads. It will also show that the granular ground substance 

 is divided, by point lines, into polygonal areas, with one of the trans- 

 parent germinative vesicles near the centre of 

 each. In fragments of very thin sections these 

 bodies separate along the lines, and each is 

 then seen to be an egg, with a layer of granular 

 yolk flattened by the pressure of adjacent eggs, 

 and a transparent germinative vesicle and re- 

 ticulated nucleolus. A longitudinal section 

 shows that these eggs are gradually pulled out, 

 towards the free end of the stolon, into a single 

 series, but they do not change their character, 

 Fig. 2. More magnified view ^^^ they are as truly eggs, at the earlier stages, 

 of a fragment of a very thin as they are after they pass into the bodies of the 

 sectionoftheovary of Fig.l. chain salpae. 



m surface epithelium, « ger- rj,^^ ^^^^ ^^ ^^^^ which fills the ovary is 



minai epithelium, o eggs. ^^^,.^.^^^^^^^1 ^y ^ i^y^^. ^f epithelium which is 



thin at the sides, but thick in the outer and inner surface. On the 



outer surface it is only one cell thick, and at a later stage it becomes 



