A Contribixt. to the Embif ol., Life-history, and Classificat. of tlie Dicyemids. 3 



3. The developmeut of the vermiform embryo, and the 

 origin of the germ-cells, with rémarks on endogenous cell-formation. 



4. Systematie affini ti e s of the Dicyemids. 



Chapter I. 



The Classification of the Dicyemidae. 

 Historical. 



KÖLLIKER supposed that ali Dicyemids could be included in one 

 species, for which he proposed the name Dicyema paradoxum. 



Wagener introduced two specific names , one [D. Eleclones) for 

 the Dicyemids found in Eledone moschata^ the other [D. gracile) for 

 those living in Sepia officinalis. Wagener remarks that the Dicyemids 

 of Octopus and Scinola resemble closely those of Eledone ; but he does 

 not affirm that they are to be included under the same specific name, 

 as represented by Van Beneden. 



Appended to Wagener's paper, comes a description by Claparède 

 of a species found by himself, Lachmann, and J. Müller, in Eledone 

 cirrosa , from the coasts of Norway , under the name Dicyema MìXlleri. 

 No further progress was made in the Classification of these animals until 

 the investigations of Van Beneden were begun in 1874. The result ofhis 

 observations in this direction may be seen from the table given below. 



Dicyema Köll. 



{^ 



I). tyims Ed. V. Ben. 

 Clausiana Ed. V. Ben. 



in Octopus vulgaris. 



macropus. 

 - Eledone moschata 



cirrosa. 



Sepia ofßcinalis. 

 biseì-ialis. 

 Sejnola Rondeletii. 



^. „ ^, ^^ -, \D. TFacrewm Ed. V. Ben. 



Dicyemella Ed. V. Ben. { .^ ^.r..», • /-<i 

 •^ [D. Midleri Clap. 



-r^. ■ T^n ^r T^ \ D . KülUkeriana ^A. N . Bgu . 



Dicyemma Ed. V. Ben. | 7-, « 7 i • t-i 3 ir -r. 

 ^ \D. Sckuìziana Ed. V. Ben. 



Dicyemopsis Ed. V. Ben. D. macrocephalus Ed. V. Ben. 



Van Beneden divides the Dicyemidae into four genera , and enu- 

 merates seven species, six of which appear under bis own name. I bave 

 increased the number of species to ten , and included ali in two ge- 

 nera, as will be seen from the following; table. 



in Octopus vulgaris Lamark. 

 niacropKs Risso. 

 De-Fi(ippi Verany. 



- Eledone moschata Leach. 



{Sepia ofßcinalis Linn. 

 elegans Blain. 

 Hossia macrosoma D. Ghiaie- 



- Sepia biserialis D. de Mont. 

 Scinola Rondeletii Gcsner. 



1* 



Dicyema Köll. 



fi. D. tyimsEd. V. Ben. 



2. D. Clausianum Ed. V. Ben. - 



3. D. microcephalum Whit. 



4. D. moschatuni Whit. 



5. D. truncatum Whit. 



6. D. Schulzianum E. V. Ben. - 



7. Z). «?ac?-oce/j//a/«wi E V.Ben. - 



