370 THE MiciiosoorE. 



of the earthworm are developed from eggs, whence they 

 emerge, not as Gregarinae, but as true nematodes. The 

 transformation of two Gregarinse, after a process of encysta 

 tion, into navicula-like bodies, has been fully described by 

 Bruch ; but Leiberkiihn has more carefully illustrated the 

 changes that go on, and has endeavoured to trace the ex- 

 istence of the pseudo-naviculse after they have been 

 expelled from the cyst. In the perivisceral cavity of the 

 earthworm he found large numbers of small corpuscles, 

 exhibiting amceba-like movements, and likewise pseudo- 

 naviculse, containing granules, formed from encysted Gre- 

 garine. He imagines that these latter bodies burst, and 

 that their contained granules develope into the amoebiform 

 bodies which subsequently become Gregarinae. M. Lei- 

 berkiihn shortly afterwards published another paper, an 

 which he adopts the same view, that the amoebiform 

 corpuscles of the blood of fish are Gregarines. But few 

 physiologists will feel disposed to agree with him, in 

 considering these bodies as parasites. 



Mr. E. Eay Lankester has contributed a valuable 

 and exhaustive paper on this subject ; l he observes : " I 

 have made careful examination of more than a hundred 

 worms, for the purpose of studying these questions, but 

 have succeeded in arriving at no other conclusion than 

 that certain forms of these may be the products of encysted 

 Gregarinae. The G. Lumbrici is one of those forms which 

 are unilocular, and are met with most frequently among 

 Annelids. It consists of a transparent contractile sac 

 (which has not hitherto been demonstrated to be formed 

 by more than a single membrane), enclosing the charac- 

 teristic granules and vesicle. The vesicle is not always very 

 distinct, and is sometimes altogether absent ; occasionally 

 it contains no granules, sometimes several, one of which 

 is generally nucleated. In some of these cysts a number 

 of nucleated cells may be seen, developing together from 

 the enclosed Gregarina, which gradually become fused 

 together and broken up, until the entire mass is converted 

 into these nucleated bodies, which are then evident in 

 different stages of development, assuming the form of a 



(1) E. Ray Lankester, " On the Gregarinidae found in the common Earth- 

 worm." — Micros. Trans, vol. iii. p. 83. 



