56 Thomas Henry Huxley 



quite freshly taken ; afterwards, the illumiuation arising from 

 friction is only local." 



Dealing with these creatures in the broad anatomical 

 spirit with which he had studied the Medusae, Huxley 

 shewed the typical structure manifested in the different 

 forms, and that was common to them and the Ascidians 

 or sea-squirts of the seashore. In a second paper on 

 " Appendicularia and Doliolum " he made further 

 contributions to our knowledge of these interesting 

 creatures. Appendicularia is a curious little Ascidian, 

 differing from all the others in its possession of a tail. 

 Earlier observers had obtained it on various parts of 

 the ocean surface, bnt had failed entirely to detect its 

 relationship to the ordinary Ascidians. Chamisso got 

 it near Behring's Straits and thought that it was more 

 nearly allied to " Venus's Girdle," a Coelenterate. 

 Mertens, another distinguished zoologist, had declared 

 that " the relation of this animal with the Pteropods (a 

 peculiar group of molluscs) is unmistakable"; while 

 IMiiller, a prince among German anatomists, con- 

 fessed that " he did not know in what division of the 

 animal kingdom to place this creature." Huxley 

 shewed that it possessed all the characteristic features 

 of the Ascidians, the same arrangement of organs, the 

 same kind of nervous system, a respiratory chamber 

 formed from the fore part of the alimentary canal, and 

 a peculiar organ running along the phar5'nx which 

 Huxley called the endostyle and which is one of the 

 most striking peculiarities of the whole group. The 

 real nature of the tail was Huxley's most striking dis- 

 covery. He pointed out that ordinary Ascidians begin 

 life as tiny tadpole-like creatures which swim freely by 

 the aid of a long caudal appendage ; and that while 

 these better-known Ascidians lose their tails when they 



