CHAPTER XXXV. 



TUNICATA. 



Systematic (after Herdman) : — 



Order I. Larvacea (Appendicularia). 

 Order II. Ascidiaeea. 



1. Ascidiae Simplices. 



2. Ascidiae Compositae. 



3. Ascidiae Luciae (Pyrosvma). 

 Order III. Thaliacea. 



1. Cyclomyaria (Doliolum). 



2. Hemimyaria (Salpa, Octaenemus). 



I. Sexual Reproduction. 

 1. Larvacea {Appendicvlaria). 



Very little is as yet known as to the development of Appendi- 

 cularia, since the small eggs which are discharged into the surround- 

 ing water are not easy to obtain and exceedingly difficult to examine. 

 Fol (No. 1) and Kowalevsky (treatise on Amphioxus) have, how- 

 ever, stated that the development of this form closely resembles that 

 of the Ascidiacea. The paired respiratory tubes of Append icularia 

 are formed in the same way as the first gill-slits of the Ascidian 

 larvae (p. 366), an ectodermal invagination appearing at each side and 

 a diverticulum of the pharynx growing out to meet it until the blind 

 ends come into contact, perforation taking place at the point of 

 junction. 



2. Ascidiae Simplices and Compositae 

 A. Oviposition, Fertilisation and Egg-envelopes. 



The eggs of most of the solitary Ascidians, soon after passing from 

 the oviduct into the atrial (peribranchial) cavity, are ejected into the 



