7g6 FRANK E. BEDDARD, 



cysts have approximately the same form as the free parasite. More- 

 over [it seems to be clear that the cyst (that is to say the outermost 

 celluhir cyst) may be formed when the parasite is comparatively small 

 and, therefore goes od growing pari passu with the iiicrease in sizc 

 of the contained parasite ; and this seems to go to prove that the cyst 

 is a pathological formation caused by the presence of the parasite. In fig. 9 

 is represented a young cyst in which the nucleus happcned to be very 

 distinct; it is intermediate in size between the fully developed cysts 

 (fig. 1) and the young forms (fig. 8), but comes nearest to the latter; 

 the cyst membrane has numerous nuclei, but is comparatively thin 

 and hyaline in appearance. There is a considerable space between the 

 cyst membrane and the contained parasite, which is further evidence 

 of the truth of my assumption that the cyst is a pathological formation. 

 There are some reasons which point to the conclusion that these 

 young Gregarines really retain the form which they had during life. 

 In the first place the similarity of their shape to the encysted adults 

 is remarkable; if it be assumed that the reagent used in the pre- 

 servatiou of the earthworm has caused the young free Gregarines to 

 contract unequally so as to acquire the shape illustrated in fig. 8, 

 this explanation will hardly do for the (presumably) more rigid cysts. 

 The vesiculaj seminales of the worm also contained numerous cysts of 

 the common Monocystis lumbrici or at least of some form very closely 

 allied to this. These cysts were in various stages of development; 

 some were filled with spores: in others the cyst had been only re- 

 cently formed, and the nucleus of the parasites was undivided. In all 

 these cases the cyst had the typical rounded form, and had been so 

 far unaifected by the reagent. There seems to be no particular reason 

 why the cysts of one species should be more affected by the reagent 

 and altered in shape than those of another. 



I furthermore took the opportunity of subjectiug the living 

 Monocystis lumbrici and M. magna to the influence of various reagents, 

 such as Alcohol, Corrosive Sublimate, Methyl Green, lodine and found 

 that their shape was hardly perceptibly altered by a prolongcd iiiimer- 

 sion in these fluids. 



These reasons taken together seem to me to prove that tlie shape 

 of this Gregarine is during life that which is represented in the 

 figures illustrating this paper. It is important to endeavour to prove 

 that this is so, because the shape of Gregarines usually differs cha- 

 racteristically in well marked species. At the same time the nature 

 of the cyst is so peculiar in this form , that any further description 



