OBSEEVATIONS ON THE C4REGARINES OF HOLOTHURIANS. 307 



affinity with my Gregarines from Holothuria, in spite of 

 certain differences, such as the single nucleus and the four 

 sporozoites. It is probable that not much stress can be laid 

 on these points of difference. The double nucleus in Grega- 

 rines from Holothnria is probably due, as has been pointed 

 out above, to precocious conjugation, while the number of 

 sporozoites is, of course, dependent on the number of times 

 the nucleus of the sporoblast divides, and is a character which 

 may be subject to variation. 



The author also figures and describes the adult and the 

 spores of Lithocystis Schueideri, Giard, from the coelom 

 ofEchinocardium cordatum, which certainly has a striking 

 resemblance to the Gregarines of Holothuria, both in the 

 form of the spores and sporozoites (eight in number), and in 

 the characters of the adult. In the latter M. Cuenot figures 

 a nucleus with vacuolated nucleolus, resembling closely that 

 of the forms described by me. At the narrow end of the spore 

 the author figures a truncated process, which is evidently 

 homologous with the funnel in my two species. Is it possible 

 that this process represents a stage in the development of such 

 a funnel ? 



It would appear from these facts that the Gregarines of 

 different Holothurians, Synaptids, and Echinoids have a 

 strong family likeness, and that a careful study and com- 

 parison of them would furnish valuable data towards a natural 

 classification of this class of Protozoa. 



M. Cuenot quotes frequently from a paper by Leger (^' Re- 

 cherches sur les Gregarines ^^) in 'Tabl. Zool.,^ vol. iii, 1892. 

 I have unfortunately not been able to see this paper. I 

 gather, however, from M. Cuenot that the author ^^ attributes 

 solely to the form of the spores a value" for classificatory pur- 

 poses, and '^ adjourns the generic denomination of every 

 species of which the complete cycle is not known." I think I 

 have sufficiently expressed my opinion above on the value of 

 the form of the spore for classification, and may refrain from 

 further criticism here. 



