264 GENEKAL HISTORY OF THE INFUSOEIA. 



4. The same form, but with the body more elongated, vermiform, and for the 

 first time exhibiting motion. 5. A very pretty Nematoid worm, about 0*10'" 

 long, blunt at one end, sharp at the other; the contents in longitudinal 

 streaks, as in the two preceding forms, but with the spaces between them 

 wider. Its motions are very active." 



This view of a metamorphosis being admitted, the question arises, do the 

 Gregarince become changed into Filarice ? or is it that the Filaria-like worms 

 are transformed into Gregarince ? Although at first inclined to consider the 

 former as the true state of the case, Leydig is now disposed to follow Heule 

 and Bruch, and adopt the latter view ; otherwise it would seem impossible 

 to account for the formation of the pseudo-Navicellce and " Psorospermia " 

 within the " Gregarince.^' 



KolHker has the following remarks on this subject (J. M. S. i. p. 212) : — 

 " Although the change of a FUciria into a Gregarina is not an impossible cir- 

 cumstance, before we admit such a thing it is first necessary to inquire whe- 

 ther the facts stated may not be otherwise explained. It is by no means 

 proved that the Anguillula-^e animal noticed by Henle, and termed by 

 Bruch Filaria, is really a Nematoid worm." Kolliker is more inclined to 

 regard it as an Infusorium allied to Oj^cdina, Proteus, &c. If this be the case, 

 there is nothing extraordinary in its transformation into a Gregarina, and 

 finally into a Navicella-rece^iOiQle. 



" For many reasons," says Stein (Zeitschr. iii. 1852), " the endeavour to 

 show the Gregarince to be larvae of higher animals, and especially to connect 

 them with encysted Nematoid worms, appears to be a vain attempt. Thus, I 

 am acquainted with Gregarince of such peculiar fonns that one requires a 

 very strong imagination to deduce them from Nematoiclea, or to suppose they 

 can pass into these. The encysted Nematoiclea are always found in the cavity 

 of the body of insects, never in their intestinal canal, where alone encysted 

 Gregarince are to be found." Again, the cysts of the Nematoidea of insects 

 are made up of nucleated cells, and are plainly a product of the vital activity of 

 the insects, not the exudation of the enclosed worm, while the cysts of Gre- 

 garince are produced as an amorphous secretion from the animals themselves. 

 *' If, therefore, encysted Nematoiclea change into Gregarince, or vice versa, their 

 cyst must undergo a metamorphosis which, perhaps, no one will assume, and 

 of which no observer has seen anything." 



Lieberkiihn's observations have gone far in shomng that, under usual con- 

 ditions at least, the Gregarinida are not converted into Filarice or any other 

 form of Vermes, but that their germs, after a short-lived Amoebiform period, 

 not amounting, however, to a true metamorphic stage, assume the characters 

 of their parent. Thus the cycle of development of these beings appears com- 

 plete ; the saccular animal constructs, by a process of segmentation of its in- 

 ternal substance, a host of germs, which, after breaking loose from their 

 parent and involving its destruction, emerge from their cases in a soft Amoe- 

 biform condition, and soon acquire the matui'e Gregariniform condition. The 

 Gregarinida exhibit a marked affinity with other Entozoa, particularly with 

 the Trematoda and Opcdincea ; and, as before remarked, they are allied with 

 the Amcehcea in the extreme simplicity of their stnicture. By the possession 

 of a limiting membrane (not independent or separable, indeed), they stand 

 between the mucilaginous fluctuating Amoehcea and the Ciliated Protozoa. 

 Unlike the Amoehcea, they do not receive into their substance solid particles, 

 — a circumstance explicable by their being covered by a somewhat resistant, 

 hardened lamina or tegument, which necessarily impedes that peculiar intus- 

 susception of solid matters witnessed in that familj^ 



As to habitat, the Gregarinida are parasites in the intestines of various In- 



