354 THE BEGINNINGS OF LIFE. 



various parts of the human body ; and such living units 

 seem to exist habitually in almost all varieties of lower 

 organisms. They have been encountered, for instance, 

 in the majority of insects and in many other classes of 

 Articulata ; whilst Balbiani * has also discovered them 

 amongst the Arachnida and in many fresh-water Ento- 

 mostraca. In the latter animals, and also in some 

 serpents, as Vlacovitch ascertained, the corpuscles are 

 of the same simple characters as those which exist in 

 certain diseased silk-worms; although in fishes and 

 other organisms 2 the corpuscles are often more com- 

 plex. They are then composed of a mass of granular 

 protoplasm enclosed within a resistent bivalved enve- 

 lope, having a projecting rim at the junction of the 

 valves, and two internal ovoidal projections either at 

 one or at both extremities. They multiply with great 

 rapidity, for some of the corpuscles are capable of 

 growing to fifty or one hundred times their original 

 size, so as to constitute generative bodies, which, by 

 a process of segmentation, resolve themselves into a 

 new progeny of Psorosperms just as psevdo-navicella are 

 produced from Gregarinse. 



These organisms being, therefore, so extremely 

 common, and, for the most part, so innocuous to the 

 animals which they frequent, it is somewhat surprising 

 to find them apparently producing a fatal epidemic 

 disease amongst silk-worms. It is, however, absolutely 



1 ' Journ. de 1'anatom. et de physiolog.' 1866, p. 599. 



2 Including some insects, such as Pyralis, according to Balbiani. 



