532 THE BEGINNINGS OF LIFE. 



survived had attained the adult condition^, and the 

 females presented, as is usual with the free Nematoids, a 

 few ova of relatively large size. The males were about 

 yV long by Yiroir" broad, and the females yV long 

 by ^-ig" in breadth ; whilst the largest egg seen, which 

 was at the vulva and about to be expelled, measured 

 g-Jo" long by tj4o" broad— so that the ovum of this 

 particular form of Nematoid was very much smaller 

 than the heterogenetic matrix from which the parents 

 had been derived 2. The heterogenetic cysts of de- 

 velopment, indeed, were so large that they could not 

 by any possibility have been produced within such 

 Nematoids as were developed from them. 



This mode of development of the Nematoid is most 

 interesting, and when compared with that of the Rotifer 

 affords certain well-marked contrasts. In the first place, 

 the process of decolourization took place in a different 

 manner — it was more simple and not attended by the de- 

 velopment of all those intermediate tints which usually 

 appear when the resulting mass is about to shape 

 itself into the form of a Rotifer. And in the second 

 place, the well-known process of segmentation which 

 occurs in the embryo mass of the future Nematoid 



^ Dr. Gros says that some of the specimens observed by him attained 

 the adult condition in about three weeks. The time mentioned above, 

 however, is much shorter than suffices for some of the homogenetically- 

 produced free Nematoids. (See ' Philos. Trans.' 1866, p. 611.) 



2 The great superiority in size of the heterogenetic germ may account 

 for the greater rapidity with which the large embryos so derived attain 

 their adult condition (see p. 551). 



