68 CO. Whituiiin 



Metazoa, the manner in which the couteuts of the axial cell give rise to 

 germs is so cumpletely imlike auything which is kuown tu obtain in the 

 Metazoa, as, to my miud, to justify the Separation of the Dicyemida 

 from the whole of this division.« p. 670. 



Gegenbaur (31, p. 257) has expressed the opinion that the Dicy- 

 emids belong to the »Entwickelungskreise von PlattwUrmern (Cestoden 

 oder Trematoden).« In the last edition of his '■Grundriss d. vergi. Anat.\ 

 he regards the Dicyemids as simple Metazoic forms, maintaining that 

 the Chief distinction betweeu a Metazoou and a Protozoon lies , not in 

 the plurality of cells , but in the arrangement of the cells in layers of 

 different functional value. »Der Organismus von Dicyema zeigt sich so- 

 mit als ein zweischichtiger mit fuuctioneller Scheidung der beiden 

 Schichten, davon die innere die morphologisch geringste Differenzirung 

 besitzt, indem sie nur aus einer einzigen Zelle besteht. Ob darin 

 ein primitiv er Zu stand sich ausspricht, ist jedoch dess- 

 halb nicht völlig sicher, weil die parasitische Existenz 

 der Dicyemen die Rückbildung eines mehrzelligen En- 

 toderms bedingt haben kann.« p. 72—73. 



GiARD (15, p. 461) thinks there can be no doubt that both the Or- 

 thonectidae and the Dicyemids belong to the phylum of the Vermes. 

 With reference to the question of degeneration, and the position to be 

 assigned to these two classes of parasites in the genealogica! table . he 

 remarks, — »Les Orthonectida doivent occuper dans ce tableau une 

 place inférieure aux Dicyemida. C e s d e r n i e r s s o n t é v i d e m - 

 ment très dégradés par le parasitisme. Leur Organisation a 

 dù étre autrefois bien plus élevée quelle ne le parait aujourd'hui. Le 

 tégument renferme d'une fa^on très evidente [Dicyema de la Seiche) 

 les bàtonnets si caractéristiques de la peau des Turbellariés , et Tem- 

 bryon présente un organe très complexe. l'urna; rien de pareil ne s'ob- 

 serve chez les Ort]ionectida.<-f 



Balfour (22, p. IH) observes, — »Till the further developnient 

 of the infusoriform embryo is known, it is not possible to arrive at a 

 definite conclusion as to the affinities of this Strange parasite. Van Be- 

 NEDEN is anxious to form it, on account of its simple Organisation, into 

 a group between the Protozoa and the Metazoa. It appears however 

 very possible that the simplicity of its Organization is the result of a 

 parasitic existence ; a view which receives confirmation from the com- 

 mon occurrence of the process of endogenous cell-formation in the axial 

 hypoblast celi. It has been clearl}^ shewn by Strasburuer that endog- 

 enous cell-formation is secondarily derived from cell-division ; so that 



