GAMETIC MEIOSIS IN MONOCYSTIS. 399 



intensely staining substance is conspicuous. The origin and 

 significance of these rings will be considered in a later paper. In 

 old sporoblasts a definite suture or groove runs down the sporo- 

 blast capsule on both sides from pole to pole, indicating the 

 presence of two valves and a prospective opening by dehiscence 

 (Fig. 17). 



The chromosome history of this gregarine thus does not bear 

 out the generalization made by Dobell and Jameson that zygotic 

 meiosis is probably characteristic of all gregarines. It is more 

 probable that both zygotic and gametic meiosis occur in this 

 group, the former probably in forms like Echinomera hispida 

 (Shellack, 1907) which has 5 chromosomes, in Nina gracilis 

 (Leger and Duboscq, 1909) which has 5 chromosomes, and in 

 Monocystis ovata (Shellack, 1912) which has 3 chromosomes, and 

 in other forms with similar odd numbers of chromosomes. 



LITERATURE CITED. 

 Cuenot, L. 



'01 Recherches sur 1'evolution et la conjugaison des Gregarines. Archiv. d. 



Biologic, XVII., 4. 

 Dobell, C. C., and Jameson, A. P. 



'15 The Chromosome Cycle in Coccidia and Gregarines. Proc. Roy. Soc. Biol.. 



Vol. 89. 

 Hesse, E. 



'09 Contribution a 1' etude des Monocystidies des Oligochetes. Arch, de Zool. 



Exp. et Gen. (5) Vol. 43. 

 Jameson, A. P. 



'20 The Chromosome Cycle of Gregarines with special Reference to Diplocystis 



schneideri Kunst. Q. J. M. S. 64 No. 2. 

 Leger, L., and Duboscq, O. 



'09 Etudes sur la sexualite chez les gregarines. Arch. Prot. 17. 

 Mulsow, K. 



'n Uber Fortpflanzungserscheinungen bei Monocystis rostrata n. sp. Arch. 



Prot. 22. 

 Shellack, C. 



'07 Uber die Entwicklung und Fortpflanzung von Echinomera hispida. Arch. 



Prot. Vol. 9. 

 Shellack, C. 



'12 Die Gregarinen, in Prowazek's Handbk. d. path. Protoz., Vol. I. 

 Wolters, M. 



'91 Die Conjugation etc. bei Gregarinen. Arch. mik. Anat., Vol. 37. 



