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. Tliompson."f" 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. I 



§ 5 REPRODUCTION IN THE POLYZOA. 



The class of Polyzoa (Bryozoa or Bryozoaria of Foreign 

 Zoologists) consists of minute Polype-like animals, having 

 a great prhnd facie resemblance to some of the Co^lenterate 

 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 Holot]iuriaa, according to Siebold, may form an exception. He 

 quotes Dalzell for their power of spontaneous division into two or moi-e 

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

 a similar multiplication oy fissuration occurring in Synapta Duve^rnea. 

 Compai-ative Anatomy (EchinodermataJ , § 95, note 1. 



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



X Transactions of Royal Society, Jany., 1857, and Jany., 1859. 



