58 



of the primitive cyst can be observed, but very obscurely, 

 and the two globes of the second generation only are distin- 

 guishable, surrounded by a common granular substance. The 

 globes grow little by little, at the same time that their enve- 

 lope thickens. Henceforward each of them is to be regarded 

 as a new cyst, whose contents will divide in their turn, to 

 give rise to two new globes or spheres, which will become 

 cysts of the third generation after the absorption of their 

 walls. The upshot of this is that the cysts of the Gregarinae 

 can multiply by division before giving rise to psorosperms, 

 and the manner in which this phenomenon presents itself 

 recalls comj)letely the multiplication of the cells of carti- 

 lage. There, too, the cells multiply by division, and the 

 capsules of the cartilage change little by little their character, 

 and are transformed into intercellular substance. The granu- 

 lar globes of the Gregarina-cysts may be compared to carti- 

 lage cells, and the granular matter which surrounds them to 

 the intercellular substance of the cartilaginous tissue. In 

 this mode of multiplication of the cysts the reason of their 

 rectilinear arrangement in the walls of the rectum of the 

 lobster is at once obvious. It is hardly necessary to add 

 that these observations on the multiplication of the cysts give 

 the explanation of the fact, so often observed but not yet in- 

 terpreted, of the existence of two granular masses in one and 

 the same Gregarina-cyst. 



It appears from what precedes that in certain circum- 

 stances — perhaps at a fixed period of the year — the Gre- 

 garina?, which were living freely in the intestine of the lobster, 

 migrate into the rectum. There they become encysted, after 

 having penetrated under the epithelium of the intestinal 

 walls, and these cysts multiply by division. It is not possible 

 to doubt that, after a certain time, the cysts are resolved into 

 psorosperms ; but it has yet to be found out what becomes 

 of these psorosperms, as also how the Gregarinse arrive in 

 the intestine again, and under what form they first appear 

 there. 



Note. — I inay take this opportunity of remarking that the view enter- 

 tained in the very interesting paper of my friend Dr. Van Beneden, as to the 

 cucystment of the Gregarinse, can hardly be considered as yet demonstrated. 

 It may be fully admitted that single Gregarina; do become encysted ; but 

 there are facts which lead to the supposition that two are umally thus 

 encased, and that the formation of pseudo-navicells thus presents a remark- 

 able approach to the conjugation of Algse, as remarked by Huxley. Not 

 only are two masses most commonly seen in a cyst, but in a spherical cyst 

 of Gregarina Blatlarum I found two nticleated Gk^axwik ('Quart, Jourii. 

 Microsc. Sci.,' vol. iii, new scr., pi. vii, fig. 17). The habit of attachment 



