196 RESEARCHES INTO THE STRUCTURE OF THE ASCIDIANS 



Section. The Cynthia in question has the appearance of a compound 

 form ; it does not, however, become muItipUed by gemmation Hke the 

 true compound forms, but the originally free, tailed larvK, adhere and 

 become firmly united before the withering away of their appendages. 

 The mass is therefore an aggregation of distinct individuals, not one 

 individual represented by many Zooid forms. 



The development of the muscular tissue of the tail was described, 

 closely resembling that of the muscles of the tadpole as given by 

 Kolliker. 



With respect to the structure of the test of the Ascidians, the 

 author stated that he had verified in many ne\v cases the discovery 

 of the presence of cellulose in large quantities therein made by 

 Schmidt, and extended by Lowig and Kolliker, and by Schacht. 

 In other points, the author's results differed somewhat from those 

 of these writers ; and after pointing out what he considered to be the 

 true structure, he drew particular attention to the essential identity 

 of the test of the Ascidian with true bone (if for the calcareous salts 

 cellulose be substituted) on the one hand, and with vegetable tissue 

 on the other. The physiological distinction between plants and 

 animals, which authors have endeavoured to draw, upon the ground 

 that the Ascidians do not form cellulose, but only take it from plants, 

 seems incompatible with the circumstance made out by the author, 

 that the Ascidian larvje contain cellulose while they are yet a mere 

 mass of cells contained within a structureless membrane, and totally 

 without any organ, except the tail. 



The author endeavoured to show that the Ascidians might be 

 divided into natural groups, by considering : — 



1st, The arrangement of the organs with regard to the axis, 

 whence the animal may be symmetrical or asymmetrical, according 

 to the relative development of the neural and hjemal regions, and of 

 the branchial sac ; and, 



2ndl)^ The nature of the tentacles and of the reproductive organs. 



In conclusion, the author stated that the Ascidian type appeared 

 to be sharply defined from all others, nowhere exhibiting any 

 transition forms. 



