525 



The Development of a Parasite of Earth-worms. 

 By John Westeay Cropper, M.B., M.Sc, Liverpool. 



(Communicated by Sir B. Eoss, K.C.B., F.E.S. Beceived June 20, 1912.) 



(From the Laboratories of the John Howard McFadden Eesearch Fund, Lister 

 Institute.) 



[Plate 14.] 



While carrying out experiments on the artificial induction of cell-division, 

 I had occasion to examine the seminal vesicles of the common earth-worm, 

 when I noticed that certain epithelial cells contained within their cytoplasm 

 structures similar to those known as " Kurloff s bodies " found in the blood- 

 cells of guixiea-pigs. 



These Kurloff s bodies have recently been shown to be parasites, to which:, 

 the name of Zymphocytozoon cobayce has been given. In their early stages, 

 they are parasites of the mononuclear cells (lymphocytes) of the blood of the 

 guinea-pig. As described in the paper on the subject (E. H. Boss, 1912), 

 they undergo development in definite stages in the lymphocyte, and 

 ultimately become free-swimming spirochsete-like bodies in the blood-plasma. 

 Having assisted in the investigation of the development of these so-called 

 Kurloff s bodies, I was struck with the similarity between them and the new 

 structures seen in the epithelial cells of the seminal vesicles of the earth- 

 worm, and the matter was further investigated. I am now convinced that 

 these structures in the earth-worm also represent phases in the life-cycle of 

 a new parasite which is very similar in its developmental figures to 

 Zymphocytozoon cobayce. 



The cells in the worm which contain these peculiar structures are the 

 large coelomic epithelial cells which form the walls of the vesicular seminales 

 of Zumbricus terrestris. The body first observed was a large spherical sac 

 containing a closely woven skein, staining deep blue with azur stain, lying 

 embedded within the cytoplasm of the epithelial cell. The method of 

 examination employed was that devised by H. C. Boss (1910) for the 

 examination of blood-cells in vitro, and it is known as the "jelly method." 

 A 2-per-cent. solution of agar in distilled water is boiled, sterilised, and 

 filtered. To 5 c.c. of the filtrate is added 1 c.c. of a 1-per-cent. solution of 

 azur II, and the total bulk of the mixture is made up with water to 10 c.c 

 in a test-tube. When molten, a small quantity of the jelly is allowed to 

 spread itself in a thin film on a microscope slide, where it will set when it 

 c ools. A drop of a suspension of the cells of the seminal' vesicles in citrated 



