58 PROFESSOR E. RAY LANKESTER, 



into spores (correspondiug to the pseudonavicula? of other 

 Gregarina;), which in turn break up into bundles of ''falciform 

 corpuscles." These falciform corpuscles are set free from the 

 spore-case and from the cyst, and exhibit active contractions 

 (woodcut, fig. 2 c, D, E, F, g). According to Eimer, the falciform 

 corpuscles are capable of assuming an amoeboid form, but it is 

 probable that under natural conditions they penetrate the cells 

 of the tissues of the Mouse before assuming a change of form, 

 which brings them to the condition of the spherical Gregariua 

 from which they started. 



It is the merit of M. Aimee Schneider to have refuted the 

 observations of Lieberkiihn, according to which the '^pseudo- 

 navicula " or " spore " of the Monocystis lumhrlci gives exit to an 

 amoeboid particle, and to have shown (by the use of the modern 

 method of osmic acid fixing and picro-carmine staining) that, on 

 the contrary, just as in Elmer's Coccidiuin, each of the spores 

 formed by the encysted Gregarina breaks up into six or a less 

 number of falciform corpuscles very closely similar in form to 

 those observed by Eimer. These falciform corpuscles — the 

 young stage of the Mouoci/stk lumhrici — are nucleated and pro- 

 bably pass by direct development into the adult form. 



But as we have seen, they often exhibit the habit of cell- 

 parasitism observed in Elmer's Coccidium, and pass when in 

 the falciform phase of growth into the substance of the young 

 sperm cells or epithelial cells of their host. 



A. Schneider has described further, and figured the formation 

 of identical falciform corpuscles in the spores (pseudonaviculse) 

 of Monocystis terebelhe and of M. nemertis. 



I have recently observed a similar formation of falciform young 

 in the naviculoid spores of the Monocystis parasitic in T/ialassema 

 Nejitiini, Gaertuer — and have moreover found the young Mono- 

 cystis as a cell-parasite within the epithelial cells of the intes- 

 tine, as also in one specimen within the ova in great numbers. 



Biitschli (loc. cit.) has recently described important cases of 

 cell-parasitism on the part of the young of Gregarma blattarnm 

 and of a Gregarina occurring in the intestine of LWiohius forfi- 

 catus. In both cases the young Gregarinse were observed 

 within the cells forming the lining of the alimentary tract. 

 Biitschli has carefully figured the spores of G. blattanim, and it 

 seems doubtful whether such exceedingly minute spores as these 

 give rise to more than one "falciform embryo.'' On the other 

 hand, in the case of Lltlwbius forficatus he observed groups of 

 falciform bodies comparable to those formed in a spore or pseudo- 

 navicula of a Monocystis. It is probable that they were not 

 related to the large Gregarina of Lithobius, but to the Mono- 

 cystid Adelia ovata discovered in that animal by A. Schneider. 



