386 GARY N. CALKINS AND RACHEL C. BOWLING. 



cystis sclmeideri (Dobell and Jameson, 1915). This joint paper 

 was followed later by individual papers on each of the two types 

 (Dobell, 1925; Jameson, 1920). In both of these types the 

 authors found that the progametic divisions are all alike including 

 the last or gamete-forming division, in having nuclei with the 

 same number of chromosomes, and that this number is the same 

 in all of the vegetative stages. The zygotes, alone of all cells of 

 the vegetative cycle, have the double or diploid number of 

 chromosomes. Meiosis or reduction in number of chromosomes 

 takes place with the first mitotic division of the zygote, a type 

 known as zygotic meiosis. The individuals which one ordinarily 

 encounters of these two species are therefore haploid as regards 

 chromosome number. 



From these findings Dobell and Jameson make the generali- 

 zation that zygotic meiosis is probably universal in Gregarinida 

 and Coccidia and they interpret Mulsow's account of reduction in 

 Monocystis rostrata as evidence of confusion by him of two species 

 of Monocystis, one with eight the other with four chromosomes. 

 It seems a little premature to say the least to sweep away contra- 

 dictory evidence in this fashion when a re-examination of 

 Monocystis in the light of Dobell and Jameson's work would 

 clear up the matter. The cytological results of such a re- 

 examination are presented herewith. 



There are many species of Monocystis in earthworms some of 

 which are apparently limited to certain species of worms. We 

 have restricted our investigation to the parasites of the seminal 

 vesicles of one species Lumbricus terresiris. Here several species 

 of monocystid gregarines are found, some almost invariably 

 present, others less frequently. We have frequently encountered 

 the large form with a proboscis-like end which undoubtedly 

 corresponds with Mulsow's Monocystis roslrata (450 fj. long by 

 220 fj. broad). We have not seen the long thread-like form which 

 Hesse names Nematocyslis magna (Monocystis magna Schmidt) 

 and is said to be from 4.5 mm. to 5 mm. long and only 50 ju in 

 diameter. We have not seen Monocystis striata Hesse with its 

 longitudinal grooves and striations which are described as 

 frequently prolonged posteriorly to form a tuft of filaments as in 

 the genus Zygocystis. We often find Monocystis agilis which can 



