34 CO. Whitman 



and raany germ-cells ; a larger number of 

 iudividuals contaiiiing no embryos, but 

 crowded germ-cells, with 1 to several large 

 free nuclei in th axial cell. 

 Apr. 26. E. mnschata 940 grms. D. moschatmn , abundant, mostly Rhombo- 



gens. Only a few Nematogens containing 

 vermiform embryos. A considerable number 

 of young Rhombogens, and individuals in- 

 closing only crowded germ-cells. Most of 

 the Nematogens and those containing only 

 crowded germ-cells showed several large 

 free nuclei in the axial cell. 

 With the exception of the last Eledone, which was the largest that 

 has heen seen for several years at the Zoological Station, the larger spec- 

 iniens have weighed from one to foiir hiindred grams. Although this 

 was an exceptionally large Eledone , the Dicyemids of its renal organ 

 diflfered in no marked respect from those of the Eledone weighing 185 

 grams. These five cases illustrate a fact attested by numerous compar- 

 isons in March and April . and , so far as my notes and memory inform 

 me, by all observations of a prior date. A series of examiuations ex- 

 tending through an entire year are required in order to settle beyond 

 dispute the question of seasonal influence on the oceurrence of the two 

 kinds of Dicyemids ; but it seems to me quite certain , at least in the 

 case of Dicyema moschatum, that their relative abundance from Decem- 

 ber to April inclusive is regulated by influences of another nature. 

 What is the meaning of the parallel between the abundance of the 

 Rhombogens and the size of the Cephalopod? Are the conditions of life 

 linder which these parasites live in mature Cephalopods unlike those 

 prevailing in immature individuals? and if so, is there any causai rela- 

 tion between these unlike conditions and the appearance of Rhombo- 

 geuic Dicyemids ? 



Or is the phenomenon a cyclical one, wholly independent of the 

 age of the Cephalopod, although showing a certain degree of corre- 

 spondence to it? and in this case, is the Rhombogenic condition an 

 integrant part of the life-history of all Dicyemids ? or only a phase in 

 the life of some or all individuals of certain generations i* Is it an inti'O- 

 ductory, or a concluding phase? 



As the succeeding pages will show, I have succeeded in obtaining 

 answers to only a few of these questions. 



The Axial Cell. 

 At a very early date in my study, I became aware of the fact that 

 the axial cell is often plurinuclear , not only in Rhombogens but also in 



