A Contiibut. to the Embryol., Lite-history, and Classificat. to the Dicyemids. 27 



from any thus far described , is shown in figs. 44, 45, and 47, PI. 4. 

 The difference in general aspect between the fully developed embryo 

 (fig. 47) and the adult (figs. 44 and 45) is trifling compared with what 

 we bave seen in most species of the octamerous type. 



The inequality between the axis and the diameter of the calotte is 

 greatest in the embryo, while the disparity in volume between the pro- 

 polars and the metapolars is greatest in the adult , ali of which is due 

 to the fact that the metapolars enlarge at a much more rapid pace than 

 the propolars. 



With respect to the number and the disposition of the cells (com- 

 pare fig. 46 which represents both ranges in optical sectìon), I find Van 

 Beneden's Statements perfectly correct: »The polar cells of the first 



range are four In the second range there are five cells, and these 



are much larger than those of the first range , and their aspect is very 

 different. Of these five cells two are ventral. Of the three dorsal, one 

 is median and two lateral.« p. 18. I can not say that the two ventral 

 propolar cells are uniformly smaller than the two dorsal, as Van Be- 

 NEDEN maintaius. The metapolars are sometimes equal in length 

 (fig. 44) , and sometimes the three dorsal cells are a little longer than 

 the two ventral ; but in either case the calotte maintains the same orthot- 

 ropal Position. In some cases I find the calotte almost free from gran- 

 ules , in others the propolars more granular than the metapolars , and 

 agaiu both sets more granular than the body. 



In fig. 47 (seen from the side) the parapolars are lateral and the 

 caudals dorsal and ventral ; now if the alternation in tlie successive pairs 

 was always one of 90 " , the caudals would agree with the parapolars in 

 being lateral. As the figure shows, the alternation follows a sinistrai 

 spirai line which sweeps an are of 90°, in passing from the anterior to 

 the posterior end of the body. The same peculiarity is often more mani- 

 fest in adults , and is not confined to this species. In nearly ali long 

 Dicyemids the elongated ectodermal cells show, individually, a more or 

 less marked spirai curvature. 



9. Dicyemennea Mülleri Clap. 



This species was found by Claparède, Lachmann, and Joh. Müller 

 in Eledone cirrosa on the coast of Norway. Neither the figures nor the 

 descriptions given by Claparède and Lachmann enable us to say with 

 certainty that this species is not the same as the one just described. It 

 is said to vary much in form. »Sometimes it is a long filament, every- 



