THE HEMIMYARIA (SALPIDAE). 



417 



of the nucleus near the oesophagus (Fig. 206) and is surrounded by 

 ramifications of the circum visceral network of blood-vessels. The 

 oviduct also appears to be accompanied until near its aperture by 

 a vascular network (Fig. 207 B, />). The point at which the oviduct 

 opens (Fig. 206, x) 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, rj.)) and projects slightly inward (Fig. 207 B, ep). This 

 swelling is the rudiment of the epithelial prominence of SALENSKY 

 which TODARO calls the uterus. 



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 SALENSKY'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 Sal}>a zonaria (CHAMISSO and ESCH- 

 RICHT), S. TJnh'Nii (KROHN) and S. hexa<j<i 

 (TRAUSTKDT), 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 

 fiiibryo, LEUCKART (No. 98) concluded that 

 several egg-follicles with distinct ducts must 

 t>e present. These forms have recently been 

 united to form the genus lasts (LAHILLE, 

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

 generic characters. 



In many of the Saty'idae (S. maxima, S. 

 /itniuild, ,S. />iinctta) the follicle appears to 

 be incompletely divided by a longitudinal 

 furrow (Fig. 207 B), into two chambers, one 

 of which (the oi'firitin sac, <>v) contains the 

 egg during the stages of its maturation, while 

 the other (the onhri/nnic sac, em) receives it 

 during the first embryonic stages. In many 

 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 



EE 



FIG. 208. Dorsal aspect of Salpa 

 bicaudata (original), a, point 

 at which this individual is 

 connected with its neighbour 

 in the chain ; e, atrial aperture ; 

 end, endostyle ; f, periphar- 

 yngeal band ; g, genital tube ; 

 i, branchial aperture ; k, gill ; 

 //, nerve-ganglion ; nn, nucleus. 



