308 BULLETIN OF THE 



The egg is inclosed in a capsule of small epithelial cells (see Fig. 

 10), which are in direct contact with the surface of the yolk, and upon 

 the lower surface of this capsule there is a long stem or gubernacu- 

 lum, which passes down the side of the body of the zooid in the 

 sinus between the branchial sac and outer tunic, and is attached to 

 the wall of the branchial sac, upon the right side, near the heart. 

 According to the observations of H. Midler (Ueber Salpen. Zeitsch. 

 f. wiss. zool. IV. 3), " the stalked capsule which, in all new-born 

 Chain-salpas, encloses the egg, is an evagination from the wall of the 

 branchial sac, and the epithelium of the latter is directly continued 

 up the stem and over the yolk " ; but I was unable to trace the epi- 

 thelium on to the guberuaculum, which seems to be a solid rod of 

 protoplasm, passing through the wall of the branchial sac and pro- 

 jecting into its cavity. At the point where the gubernaculum joins 

 the wall of the branchial sac, the latter is slightly depressed, so as to 

 form a cup with its convex surface turned towards the branchial cav- 

 ity, so that the cavity of the cup, which is to form the " brood-sac," 

 is a diverticulum from the sinus system ; and blood-corpuscles may 

 usually be found within it, as well as upon the sides of the gubernacu- 

 lum, adhering together so as to form irregular clusters, as shown in 

 Fig. 9.* 



Very soon after the chain is discharged into the water, the egg 

 undergoes impregnation, which, however, is not effected by the sper- 

 matic fluid of the zooid which contains the egg, nor by that of any 

 other zooids in the same chain. The testis, at this time, is in a 

 very rudimentary state (see Figs. 33 and 34, /), and does not become 

 developed until after the solitary embryo into which the egg is devel- 

 oped has been discharged from the body. Wherever Salpa is found 

 at all, it is very abundant, and individuals at all stages of growth 

 occur together, so that some portion of the fluid discharged into the 

 water from the testis of an adult male readily finds its way into the 

 cavity of the branchial sac of the young male which carries the unim- 

 pregnated ovum, and numbers of actively moving spermatic filaments 

 may be found within this cavity at this time. These filaments seem 

 to be drawn to the exposed tip of the gubernaculum by some attrac- 



* Leurkart (p. 47) describes this cup as a solid organ developed upon the wall of the 

 branchial sac; although he refers to Vogt's correct description of it (Bilder aus dem 

 Thierleben, S"J). 



