58 ANATOMY AND PHYSIOLOCiV OF SALPA AND PYROSOMA 



in a papilla, like that of the vas deferens, projecting into the post- 

 branchial cavit}'. 



In }-oung specimens, when the ovum is small and the yelk pale, this 

 gubernaculum frequently appears to be solid ; but in fully-grown 

 specimens, when the ovum has its full size, and the yelk is darker 

 and granulous, it presents the appearance of a wide tube, especially at 

 its upper part. And here there was frequently an appearance of dark 

 stria; and moving granules, prompting the belief that spermatozoa had 

 travelled thus far. 



In one instance (fig. 6) the sac of the ovum was empty and the 

 gubernaculum or duct widely distended. The appearance of sperma- 

 tozoa in the duct was here very strong, fig. 5. 



None of the compound ova described by Savigny were present in 

 the specimens of Pyrosoina examined. 



56. The young polypes described by Savigny as existing between 

 the fully-formed ones, in all stages of development, are formed by 

 gemmation, Plate XVII. [Plate 7] fig. 7 q. 



A diverticulum of the dorsal sinus of the parent is formed just 

 above the heart ; the extremity of this diverticulum thickens and 

 enlarges, and assumes the form of a single zooid. For a long time a 

 vascular connection is maintained between it and the parent, by means 

 of a duct, in which there seemed to be traces of a longitudinal parti- 

 tion, as in the gemmiferous tube of Salpa. Ultimately the connection 

 appears to cease, and the two polypes live on independently. 



It is to be remarked, that while in Salpa the ventral side of the 

 young bud is first marked out, and the communication of the parent 

 with the young is thence on the dorsal side of the foetus, in Pyrosoma 

 the dorsal side is first developed, and the communicating canal opens 

 on the ventral side of the }-oung. 



57. The ovum or ova, for there are sometimes two or three, are per- 

 ceptible very early in the young polype produced by gemmation, and 

 are then situated in the middle line posteriorly. 



58. The muscular system is best seen in a young specimen (fig. 8 k). 

 Two very delicate bands encircle the inner tunic anterior to the gang- 

 lion. From the posterior extremity of the ganglion two strong bands 

 arise, which diverge for about half the distance between the ganglion 

 and the mouth. Here they divide into two branches, one of which 

 continues the original direction, while the other meets its fellow just 

 behind the mouth. The former, as it leaves the under surface to be- 

 come lateral, is much increased in size, and eventually terminates at a 

 short distance from the generative glands, forming on each side the 

 band of which Savigny speaks as passing towards the Hver. 



