236 HETEROGENETIC ORIGIN 



a rule, also, so far as I have seen, these matrices only rarely 

 undergo segmentation ; so that in regard to their mode of origin, 

 their gradual growth, their formation of thick cysts, their quies- 

 cence for comparatively long periods, as vpell as this rarity 

 of segmentation, the secondary matrices present characters 

 strikingly different from those of the matrices that are developed 

 primarily and directly from the pellicle itself — that is from aggre- 

 gates of Bacteria forming therein. 



I have, as a rule, seen two different kinds of cysts in these 

 matrices of amoeboid origin ; one of them being thick and brown 

 in colour, and having the surface covered by brown, rounded 

 knobbles. These have often been found in, or on, the under 

 surface of old hay pellicles, somewhere between the fourteenth 

 and the twenty-eighth days, and they vary much in size, as may be 

 seen from Fig. 50, A ( x 37S), in which there is also represented an 

 embryo, contracted under the influence of formalin, which had just 

 escaped from another of these cysts. The second form of these 

 cysts, and the kind which is much the more common of the two, has 

 not the same dark brown tint, but it has a wrinkled or plicated 

 appearance, such as may be seen under a low power in B ( x 200). 

 The formation of a cyst of this kind is common even in the segments 

 into which the primary matrices divide, if the condition of the 

 infusion becomes unfavourable to their existence in a free state. I 

 have recently seen a large number of such matrices, each of whose 

 contents divided into two active embryos ; but, conditions becoming 

 in some way unfavourable, they speedily came to rest, and each 

 segment assumed a spherical form within the thin original cyst. 

 Two days later I found large numbers of these segments in plicated 

 cysts, rather than bounded by thin, smooth membranes as they had 

 been previously (C, X 250) ; and often, of two contained within the 

 same cyst, one had become thus changed, while the other was still 

 enveloped merely by the thin and smooth membrane that forms 

 when the segment first assumes a spherical shape. 



So far, I have been speaking of the origin of matrices from 

 amoeboid corpuscles in the pellicle itself, where they commonly 

 occur intermixed with others derived directly from its substance. 

 I now have to speak of their appearance in the villi which, in an old 

 infusion, are apt to grow downwards from the pellicle.' Here, 



' That is, where the pellicle is thick, owing to its being formed on an infusion 

 four or five inches in depth. A thin pellicle will not develop villous growths. 



