4Y6 



Report of the State Geologist. 



now its full form and breaking free from the funiculus,^lies free 

 in the perigastric space. 



Fig. 31. A fully developed statoblast, frond and side view (after Allman) . 



" When exposed to conditions favorable to its development, the 

 two faces after a longer or shorter period separate from one 

 another and a young polyzoan gradually emerges and floats 

 away freely through the surrounding water. The surface of 

 the young polyzoan thus become free is destitute of cilia except 

 on the tentacles, and the motions of the young animal seem to be 

 quite passive, except as they may be influenced by the cilia on 

 the tentacles. At the period of its escape it possesses all the 

 essential organization of the adult. The retractor muscles are 

 well developed and the polypid is capable of regular exsertion 

 and contraction, but the ectocyst is colorless and transparent 

 and free from the earthy particles which in the greater number 

 of species are afterward formed in it, and the little animal is 

 still simple. It loses no time, however, in developing gemmae, 

 which soon change it to the compound form of the adult. 



" The general structure of the statoblasts being now under- 

 stood, the important question at once suggests itself. What is the 

 true importance of these bodies ? All that we have seen of them 

 is manifestly in accordance with the nature of a bud. The 

 invariable absence of a germinal vesicle and germinal spot, and 

 their never exhibiting the phenomena of yelk cleavage, inde- 

 pendently of the conclusive fact, that true ova and ovary occur 

 elsewhere in the same individual, are quite decisive against their 

 being eggs. We must then look upon them as gemmce peculiarly 

 encysted and destined to remain for a period in a quiescent or 

 pupa-like state. It was for this reason, therefore, that I pro- 

 posed for them the name of statoblasts — Izaro- jSMffry].^^ 



