236 



THE ASCIDIANS. 



Jit 



ance, doubles up obliquely forwards to the left atrial 

 chamber, into which it opens by the anus (Fig. 107). 



In the angle made by the outgoing intestine with the 

 stojiiach, a blind diverticulum arises. It is at first a sim- 

 ple ccecum, but soon begins to branch (Fig. 105 C\ and 

 finally forms an arborescent growth embracing the in- 

 testine (Fig. 107). This is the so-called pyloric gland, 

 and it is probably homologous with the hepatic ccecum of 

 Amphioxus. 



Appendicularia. 



It is generally agreed among those who have a voice in 

 the matter, that most of the pelagic Ascidians (Salpa, 



Doliolum, Pyrosoma) are 

 highly modified forms, spe- 

 cially adapted to a pelagic 

 life, one of the results of 

 which is that their repro- 

 duction is marked by a 

 complicated alternation of 

 generations. 



It would, therefore, not 

 assist us in our comparison 

 with Amphioxus to describe 

 these types. 



There is, however, one 

 family of pelagic Ascidians, 

 the Appendicnlaria, with re- 

 spect to which there are two 

 widely different opinions. 



Fig. in. Appendicularia (Fritii- The Appendicularias are 



/aria) furcata, from the ventral surface. n . . . A 



(After LANKESTER.) pelagic, free-swimming As- 



a.Anus. gl. Unicellular glands, gj. c idianS, whose adult COndi- 



Gill-slits. h. Dorsal hood-like fold of 



integument. ;. Mouth. /. Tail. 



tion is so far similar to the 



