POTTSIELLA ERECTA. II5 



sparsely filled series of quiescent setae, in strong contrast with 

 the rapidly moving cilia around them. 



The development of this polyp from the ovum, of which 

 interesting hints have been obtained, and its internal struc- 

 tural peculiarities, are reserved for further study, and if satis- 

 factor}' results shall have been attained, the}' will be treated 

 of in a later paper. The nearly simultaneous observation of 

 this species in three distinct localities, and its abundance in 

 each, indicates that it is probably not uncommon, and excites 

 surprise that it does not appear to have been previously noticed. 



Mr. Potts now adds the following : — 



As the above-named Paliidicella erecta does not appear in 

 the work of Dr. Allman, or of any other writer upon the 

 Fresh- water Bryozoa, it may be worth while to explain that 

 when specimens of this form were sent, amongst other Amer- 

 ican species, to Professor Karl Kraepelin, of Hamburg, Ger- 

 many, in response to his request, he determined after careful 

 examination of the living material that " this species shows 

 characters differing so widely from those of Paludicella that 

 it cannot be permitted to remain in that genus," nor in any 

 other as yet described. He therefore proposed "a new genus, 

 under the name Pottsiella, in honor of its discoverer." He 

 alludes in his beautiful monograph upon the "German Fresh- 

 water Bryozoa," as does the above extract, to the substitution 

 of hybernaculae as methods of conservation and reproduction, 

 in place of the familiar statoblasts of most other Bryozoans. 

 The summer ovae, referred to above, were again seen some 

 years later, and figures representing them may be seen, Nos. 

 4 and 5, on Plate No. 4, in Proceedings of the Delaware 

 County Institute of Science, Vol. Ill, No. 3. 



