24 C. 0. Whitman 



that there are eight polar cells; bnt cannot affirm positively 

 that they are arranged precisely as in D. truncatum. I have 

 never seen any individuals with large caudal cells. The 

 length ofthis species agrees nearly with D. truncatum. 



7. Dicyema macrocephaluni E. V. Ben. Figs. 35 — 39, PL 3. 



Follndonlyin-6'e^.>^o/ai2owG?e/e^^^G^esner. 



Calotte octamerous; almostconstantlyplagiotropal; 

 presenting a flattened, more or less circular, or some- 

 what quadrilobate face; broader than the body, and 

 expanding into a free plate-like margin. Thesub-equal 

 propolars form the central portion of the cephalic piate, 

 and the slightly uneqnal metapolars its free margin or 

 rim. Each set of polar cells presents two ventral and two 

 dorsal cells, the cells of one set being opposite the cor- 

 responding cells of the other set. The two lateral para- 

 polars, somewhat thickened at their junction with the 

 calotte, are foUowedbythree ec toder mal cells — 2 dorsal 

 and I ventral. 



The ectodermic cells disposed in 6 alternating sets 

 of 3 cells each, interposed between the parapolars and 

 the 2 caudal cells. 



Verruciform cells — 5. 



Total number ofectodermal cells 30. 



Length 5 — 7mm. 



Van Beneden has represented the calotte of this species turned 

 450 out of its natural position (compare his figs. 3 and 5, PL 2, with my 

 fig. 37, PL 3), and this displacemeut introduces features that appear to 

 separate it from all other octamerous calottes. Again, he is equally un- 

 fortunate in affirming that there are f u r parapolar cells instead of two 

 as in all other Dicyemids. If Van Beneden were correct in these two 

 points, I should be free to admit the necessity of forming a new genus; 

 but he is certainly wrong in both, and the error may probably be attrib- 

 uted to a too hasty examination of unfavorable examples. 



I have seen cases in which the calotte appeared to be in precisely 

 the same position Van Beneden has given it ; but a study of the younger 

 stages and a comparison of a large number of adult forms have 

 shown that in each set of polar cells two are ventral and two dorsal. 

 To make certain of this point, I have examined specimens alive, and 



