IN THE ANIMAL KINGDOM. 87 



of a process of this kind.* Nor have we any remarkable 

 structural metamorphosis in this stage, except in the pe- 

 dunculated species, some of which at least are known after- 

 wards to become free by separating from the calcareous 

 stem. In this way the so-called Pentacrinus Europeus is 

 converted into the Comatula rosacea, as was first discovered 

 by Mr. J. V. Thompson.-)- From the later observations of 

 Prof. Wyville Thomson it appears that the young Echino- 

 derm formed from a barrel-shaped zooid, like that of a 

 Holothuria is at first a free egg-shaped body ; by the 

 elongation of the narrow end it then becomes club-shaped, 

 and the pointed extremity attaches itself by a disc of 

 cement matter to some foreign body. The consolidation of 

 the pedicle by the deposit of calcareous matter in its tissue 

 at intervals gives it subsequently a jointed character. The 

 rays or arms are of later growth, and do not acquire their 

 full development till close on the period of the detachment 

 of the body.J 



5 REPRODUCTION IN THE POLYZOA. 



The class of Polyzoa (Bryozoa or Bryozoaria of Foreign 

 Zoologists) consists of minute Polype-like animals, having 

 a great primd facie resemblance to some of the Coelenterate 

 type, and having also, like them, a great tendency to the 

 development of zoophytic or composite forms. Popularly 

 they both go under the name of polypes, and even by zoolo- 

 gists they were confounded till a recent period. The 

 Polyzoa, however, have a much higher organization than the 



* The Holothuriaa, according to Siebold, may form an exception. He 

 quotes Dalzell for their power of spontaneous division into two or more 

 parts, each of which may become a complete animal, and Quatrefages for 

 a similar multiplication Dy fissuration occurring in Synapta Duvernea. 

 Comparative Anatomy (Echinodermata) , 95, note 1. 



f Edin. Philosoph. Journal, for April, 1836, p. 296. 

 . t Transactions of Eoyal Society, Jany., 1857, and Jany., 1859. 



