CHAPTER II. 



UROCHORDA 1 . 



IN the Solitaria, except Cynthia, the eggs are generally laid, 

 and impregnation is effected sometimes before and sometimes 

 after the eggs have left the atrial cavity. In Cynthia and most 

 Caducichordata development takes place within the body of the 

 parent, and in the Salpidae a vascular connection is established 

 between the parent and the single foetus, forming a structure 

 physiologically comparable with the Mammalian placenta. 



Solitaria. The development of the Solitary Ascidians has 

 been more fully studied than that of the other groups, and appears 

 moreover to be the least modified. It has been to a great 

 extent elucidated by the splendid researches of Kowalevsky 

 (Nos. 18 and 20), whose statements have been in the main 

 followed in the account below. Their truth seems to me to be 

 established, in spite of the scepticism they have met with in 

 some quarters, by the closeness of their correspondence with 

 the developmental phenomena in Amphioxus. 



1 The following classification of the Urochorda is adopted in the present chapter. 



I. Caducichordata. 



( Solitaria ex. Ascidia. 



A. SIMPLICIA \ 



{ Sociaha ex. Clavdhna. 



B. COMPOSITA Sedentaria ex. Botryllus. 



Natantia ex. Pyrosoma. 



( Salpidse. 



C. CONSERTA < 



( Doliolidse. 



II. Perennichordata. 



Ex. Appendicularia. 



