OBSERVATIONS ON POLYZOA. 201 



man, and Mr. Albany Hancock.* These experienced 

 naturalists surveyed the whole field, and, armed with pow- 

 erful modern microscopes, they completely disclosed the 

 anatomy and physiology, making nearly all preceding ex- 

 plorations interesting only as matters of history. 



Dr. Leidy is the sole authority upon this subject in 

 America.f His observations have given us all. the informa- 

 tion we at present possess of our native species, besides 

 adding two new and singularly interesting genera, Pec- 

 tinatella and Urnatella, to the systematic catalogue. Of 

 these two, Pectinatella alone belongs to the Phylactolee- 

 mata. 



Nothing of a general nature having been published in 

 this country, it may, perhaps, be well, before proceeding 

 with the structural analysis of the Phylactolsemata, to give 

 a sketch of the classification and a description of the dif- 

 ferent forms of this suborder. 



The Polyzoa, for a long time confounded with the Radi- 

 ata, were first definitely separated by Thompson in 1830, 

 and called by him Polyzoa, thus taking precedence of 

 Bryozoa, the name afterwards given them bv Ehrenberg 

 in 18314 



In 1834, De Blainville, although still continuing to as- 

 sociate them with the Radiata, set off the genera Crista- 

 tella, Plumatella and Alcyonella as a subclass, styling 

 them "Polypiaires douteux."|| 



*Dumortier & Van Beneden. Hist. Nat. d. Polypes composes d'eau 

 douce. Nouv. Mem. de l'Acad. Roy. de Bruxelles. Vol. 16. 1843. 



Van Beneden, Recherches sur les Bryozoaires. Mem. de l'Acad. 

 Roy. de Belgique. Vol. 21. 1848. 



Dumortier & Van Beneden. Hist. Nat. des polypes com. d'eau 

 douce. Mem. de l'Acad. Roy. de Bruxelles, comp. au torn. 16. 1848. 



Albany Hancock. On the Auatomy of the Fresh-water Bryozoa, 

 with descriptions of new species. Ann. and Magazine of Nat. Hist. Vol. 

 5. 1850. 



Prof. Allman. Monograph of the Fresh-water Polyzoa. Ray 

 Society, 1856. 



fDR. Joseph Leidy. Proc. Philadelphia Acad, of Nat. Sciences, 

 Vols. 5, 7, and 10. 



iBusK. On the priority of the term Polyzoa. Ann. and Mag. Nat. 

 Hist. 2d Ser. Vol. 10, p. 352. 1852. 



|| De Blainville. Man. d'Actinologie et de Zoophytologie. p. 489. 

 Paris. 1834—37. 



