76 C. 0. Whitman 



Résumé. 



1. According- to the methodof Classification introduced by Ed. Van 

 Beneden, the generic and specific uames of the Dicyemids (Hetero- 

 cyemids excluded) run parallel with those of their hosts , genus for 

 genus and species for species. The Dicyemids found in four genera 

 of Cephalopods, Octopus^ Eledone^ Sepia and Sepiola, were divided 

 into four correspondiug genera , Dicyema , Dicyemelia , Dicyemma, 

 and Dici/emopsù ; and these four genera were said to include seven 

 species correspondiug to the same number of species of Cephalopods. 

 The correspondence here assumed as a basis of Classification is dis- 

 proved by the following facts : 



(i) In Eledone mos eh ata are found two species of Dicyemids. 

 Dicyema moschatum and Dicyemennea Eledones ; and in Ö e p i a o f f i c - 

 i n a 1 i s , likewise two species , Dicyema truncatum and Dicyemennea 

 gracile. 



(2) Dicyemennea Eledones occurs in two different Cephalopods, 

 Eledone Aldrovandi and Eledone moschata; and Dicyema 

 truncatum. is found in three Cephalopods, Sepia officinali s, Se- 

 pia elegans, and R ossia macrosoma. 



(3) Two closely allied species of Dicyemids, Dicyemennea Eledo- 

 nes and Dicyemennea gracile , are found in Cephalopods belonging to 

 two different families; while two widely different species of Dicyemids, 

 Dicyema truncatum and Dicyema macrocephalum, occur, singly, in two 

 closely related genera of Cephalopods (Rossia and Sepiola). 



2. The ten species of Dicyemids decribed on pages 9—29 repre- 

 sent two genera distinguishable by the number of cells in the head, or 

 calotte. 



The genus DicyemaK'óU., including seven species, has a bilateral 

 calotte coniposed of eight cells (octaraerous) , in two sets of four each 

 ipropolar and metapolar). The calotte is invariably orthotropal (p. 8) 

 in the embryo , but in the adults of most species is generally more or 

 less oblique [plagiotropal, p. 8 — 9 and il). The propolars are always 

 two dorsal and two ventral, and are opposite the correspondiug metapo- 

 lar cells, except in Dicyema truncatum where the metapolars are two 

 lateral, one dorsal, and one ventral [alternate order, p. 21—22). 



The genus Dicyemennea, including three species, has a bilateral 

 calotte constituted of nine cells (enneamerous. p. 9), four propolar and 

 five metapolar. The propolars are two dorsal and two ventral, and 



