rill: IIKMIMYAKIA (SALPIDAE). 



417 



of the nucleus near th< sophagus (Fig. 206) ami is surrounded by 



ramifications of the circumvisceral network of blood-vessels. The 

 oviduct also appears to be accompanied until near its aperture by 

 a vascular network (Fig. 207 A', b). The point at which the oviduct 

 opens (Fig. 206, .<■) is found on the right side of the body behind the 

 penultimate muscle-hoop above the nucleus. Round the aperture, 

 the epithelium of the atrial cavity is thickened into a shield (Fig. 

 207 A. '/-) and projects slightly inward (Fig. 207 A, e/i). This 

 swelling is the rudiment of the epithelial pro?ninence of Salensky 

 which TODARO calls the ul, rus. 



--/ 



-/ 



The question now arises whether the members of a Salpa-chain, after the 

 birth of the mature embryo, remain sterile or are able to produce a new ovary 

 which may yield a new embryo. Some of Salexsky's observations seem to 

 favour the latter view. The individuals composing a chain grow consider- 

 ably in size while the embryo is developing within them, so that the largest 

 individual contains the most advanced embryo. Salensky, in such a large 

 individual, found the remains of a placenta 



which indicated the previous expulsion of « 



an embryo and, side by side with this, a 

 mature egg or a quite young embryo. 



Exceptions to the rule that each individual 

 of a chain produces only one embryo are 

 found in Salpa zonaria (Chamisso and P^scn- 

 richt), .S'. Thilesii (Kbohn) and S. hexagona 

 iTraustedt), in which several embryos 

 develop simultaneously, although they are 

 not all at the same stage of development. 

 In consequence of this and of the presence 

 of a special point of attachment for each 

 embryo, Lf.uckart (No. 98) concluded that 

 several egg-follicles with distinct ducts must 

 be present. These forms have recently been 

 united to form the genus Iasis (Lahii.i.i . 

 No. 38), the above feature being one of its 

 eric characters. 



In many of the Salpidae {S. maxima, S. 

 pinnata, S. />/tiut<it<i) the follicle appears to 

 he incompletely divided by a longitudinal 

 furrow (Fig. 207 />'). into two chambers, one 

 of which (the ovarian sac, ov) contains the 

 egg during the stages of its maturation, while 

 the other (the embryonic sue, cm) receives it 

 during the first embryonic stages. Inmate, 

 forms (e.g., S. maxima) the embryonic sac is 

 continued into a pointed process (s) which 



soon degenerates. The remains of this process, in later stages, when the 



KE 



f 





Fig. 208. — Dorsalaspecl of Salpa 

 Mcaudata (original). ". point 

 .it which this individual is 

 connected with its neighbour 

 in tin- chain : e, atrial aperture : 

 end, endostyle : ./'. periphar- 

 yngeal band ; g, genital tube . 

 i, branchial aperture ; /.•, Kill ; 

 n . nerve-ganglion ; nu, nucleus. 



