A Contribution to the Embryology, Life-history, 

 and Classification of the Dicyemids. 



By 

 e. 0. Whitman. 



With Plates 1—5. 



Since the discovery of the stränge parasite« of the renai organ of 

 Cephalopods, by Kroiin, in 1 839 ' , they have been stiidied by Erdl, 

 KöLLiKER, G. Wagener, Claparède, J.Müller, Ray Lankester, 

 P.J. Van Beneden, and Ed. VanBeneden and his pupils, Foettinger 

 and MoREAU. It was Kölliker who first made kuown the highly inter- 

 esting fact that these animals produce two kinds of embryos, and who, 

 for this reasou, gave them the name Dicyema'^\ but it is Ed. Van Be- 

 NEDEN to whom we are chiefly indebted for what has thns far been 

 aseertaiued coneerning their embryology, Classification, and systematic 

 affinities. 



It is quite unnecessary to give here the usuai historical survey of 

 results reached by previous investigators, as this has already been done 

 by Van Beneden : and it would certainly he superfluous to ofifer a sum- 

 mary of the researches on this subject by Van Beneden himself , since 

 every naturalist is familiär with his memoir on the Dicyemids, and most 

 of our zoological text-books contain an epitome of the facts and con- 

 clusions there presented ; and ali the more so, since I shall have fre- 

 quent occasion to refer to the same , by direct citations, in the body of 

 this paper. 



The important systematic position assigned to this group of para- 

 sites by Van Beneden, and the many questions stili unanswered in re- 



* Not 1830 as has been so often stated. 

 2 dis and -AUYifjia, embryo. 



Mittheilungen a. d. Zoolog. Station zu Neapel. Bd. IV. 1 



