22 C. 0. Whitiuan 



TMs alternate order of the polar cells is quite distinct from the 

 opposi te Order seen in all the other species of the genus, and might 

 perhaps serve as a basis for the formation of a new genus ; but as I find 

 only one species thus marked, there seems no urgent necessity, at pre- 

 sent, for burdening science with a new name. 



The calotte is nearly hemispherical in the embryo , and may be 

 Said to form the entire head. These relations are very seldom seen in 

 the adults (fig. 59) , the calotte becoming, as a rule, more or less flattened 

 with age, owing to the fact that its growth does not keep pace with 

 that of the parapolars (figs. 53, 54, 57). 



Van Beneden estimates the number of ectoderma! cells at 25. 

 Although I am certain that he has counted one too many in the calotte, 

 1 am not equally so that he has made an error of two in the body. 

 While I have never succeeded in finding more than 22 , in specimens 

 taken from S. officinalis, S. elegans^ or Rossia macrosoma, I have seen 

 cases with only 20, and one of these is given in fig. 53. But such cases 

 are exceedingly rare , and the still greater variations, such as van Be- 

 neden has described (see his fig. 8, PI. 2), are unquestionably tobe 

 regarded as abnormal. The number 25 agrees neither with that which 

 I regard as normal for D. truncatum , nor with that of the associate 

 species, D. gracile. 



The caudal cells are generally two and symmetrically placed ; but 

 cases have been met with in which three of the terminal cells were 

 charged with granules, all presenting the sanie outward appearance 

 and forming together a trilobate euding. In some instances only one of 

 the two normal caudal cells were loaded with granules ; and frequently 

 both cells are very small and inconspicuous (fig. 52). 



I have always found this species very abundant in S. officinalis. 

 By its short and rhabdoidal form it is easily distinguished from the elon- 

 gated and slender D. gracile., which occurs in much smaller uumbers. 

 That this species is identical with that found in Rossia macrosoma and 

 Sepia elegans is , to my mind , as certain as it can be , so long as our 

 knowledge of the cycle of life of these animals remains incomplete. In 

 the first case of Rossia that was examined for the purpose of compari- 

 son , I noticed one or two peculiarities which I had not recognized in 

 specimens from S. officinalis. The calotte formed , in many individ- 

 uals (fig. 59) a large portion of the head; and the entire ectoderm, 

 with the exception of the finely granular polar cells and the large cau- 

 dal cells, was charged with coarse shining granules of an elongated 

 angular form. In every other respect, the specimens agreed precisely 



