206 Mr Perrin, Preliminary Communication on the Life-History 



within the trophozoite without any cessation of activity or growth. 

 These internal buds have been styled by Gurley pansporoblasts. 

 In Pleistophora periplanetae, however, no such production of pan- 

 sporoblasts takes place. The whole of the trophozoite simply 

 withdraws its pseudopodia, rounds itself off and makes spores. 

 As, however, the classification of the Myxosporidia is largely based 

 upon the features exhibited by the pansporoblast, the number of 

 spores it produces, etc., it seems advisable to regard the tropho- 

 zoite of Pleistophora periplanetae as producing one pansporoblast, 

 although the point at which trophozoite ceases to be trophozoite 

 and becomes pansporoblast may not be easy to define. The 

 first stage then of sporulation consists in the rounding off of the 

 trophozoite to form a pansporoblast, which is usually more or 

 less oval and almost completely filled with developing spores. 

 The spores are developed from oval masses of protoplasm, the 

 sporoblasts, which rather exceed in size the spores into which they 

 are transformed. In stained preparations each sporoblast appears 

 to lie in a vacuole. This vacuole is not, however, evident in the 

 living cell, and is probably an artifact produced by shrinkage of 

 the protoplasm during preparation. Each sporoblast contains a 

 nucleus, which is at first reticular, and stains bright red with 

 Giemsa's eosin-azur mixture. The interstices between the de- 

 veloping sporoblasts are filled up with protoplasm and nuclei, both 

 of which ultimately disappear. 



The nucleus of the sporoblast undergoes various changes 

 which will be described with figures in the full paper, and the 

 sporoblast surrounds itself with a coat of a highly resistant 

 nature. The presence of this coat makes staining the spore 

 very difficult. In its final form as found in the faeces of the cock- 

 roach, the spore is a flat oblong structure rounded at both ends, 

 and varying from 5/j, — 6/j, in length, and 2'5 — 3//. in breadth. In 

 the living state the sporoplasm is finely granular and contains at 

 one end a small highly refractive globule. The relation of the polar 

 capsule, which is almost certainly present, to this globule has not 

 been determined. Application of the usual reagents ether, con- 

 centrated sulphuric, nitric and hydrochloric acids, glycerin, iodine 

 and boiling water, etc., has hitherto failed to procure extrusion of 

 the filament of the capsule. The spore coat is apparently un- 

 affected by the above reagents and also by eau de Javelle. 



Attempts to produce the emergence of the sporoplasm by 

 treating the faeces with the digestive juices and contents of the 

 alimentary canal of other cockroaches have been unsuccessful. 



With the above facts of the life-history of Pleistophora peri- 

 planetae to hand it is possible to classify the parasite accurately. 

 From the minuteness of the spores, the fact that the pansporo- 

 blast produces more than two spores, and the invisibility of the 



