600 RECORD OF SCIENCE FOR 1886. 



like Protodrili, but with dorsal chord, and anterior respiratory diverti- 

 cula from the gut, formed the commou starting point for the Chordata. 

 In these Protochordata the posterior portion of the truuk is adapted 

 more especially for locomotion, while the caudal region of the ancestral 

 digestive tube has undergone progressive atrophy and the vegetative 

 functions have become more localized in the anterior part of the trunk. 

 The transformation of one part of the segmented body of the vermiform 

 ancestors has affected all the truuk, except the cephalic extremity and 

 first segment of the body, in those forms whence the Urochordata have 

 arisen." 



(3) " The affinities between Uro- and Cephalochordata are much closer 

 than between either and the Vertebrata." 



The manner in which tl:?. various groups have originated and the suj)- 

 posed degree of their relationship are exhibited in a scheme herewith 

 presented: 



C eplialochordata. 

 Vertebrata. 



Urochordata. 



Auuulata. 



Protochordata, 



Protanmilata. 



(Arch, de Biol., vi, pp. 237-476, 9 pi.; J. R. M. S. (2), 1887, pp. 

 62-05.) 



Classification of the tunicates. — The tuuicates have been variously sub- 

 divided into orders, but according to M. F. Laliille all of these arrange- 

 ments are more or less unnatural, and in his opinion the best basis for 

 a primary classification of the chiss is furnished by the development of 

 the gills. "The Salpidse have a single row of holes on either side of 

 their gill organs ;" the Doliolidse are similarly characterized, but the holes 

 are more developed as well as more numerous. The Didemnidse have 

 three rows, and, finally, the Leptoclinidne have four. In the "higher 

 types the gill is larger, and is placed beside the intestine. In the Tha- 

 liacea the respiratory organ is very simple and without papillae." 

 Those forms, which are characterized by a simple gill, are grouped 

 together under the name " Ai^lousobranchiata." Those in which " the 

 gill is provided with longitudinal vessels" are grouped together under 

 the name " Phlebobranchiata." Finally, those which " have longitudi- 

 nal folds on the gills" are distinguished as " Stolidobranchiata." The 

 progressive complication of the gill, it is affirmed, corresponds "to in- 

 crease in the differentiation of the whole ascidian organism," and the 

 proi)osed classification, it is urged, is therefore not the outcome of de- 

 pendence on a single character, but the result of a co-ordination of 



