172 Mr. H. J. Carter on the Conjugations of 



tions to the 'Annals/ still further support me in the views 

 therein announced, viz. that the nucleus furnishes the sperm, 

 and some other part of the body of the Difflugia the germ-cells, 

 which produce the new generation. For in that large species 

 which I have designated urceolata in my last communication, 

 and which I have since ascertained to be one of the most per- 

 sistent and plentiful forms about this neighbourhood, I, last 

 summer, almost invariably found the nucleus (instead of under- 

 going the change as a whole) to become divided into several 

 spherical cells of equal size, each of which presented bodies in 

 its interior similar to a brood of cells, which, on other occasions 

 and under similar appearances, I have found to issue in the form 

 of ciliated, monadic, polymorphic Rhizopods. With these also 

 were present a number of much larger round and sub-round 

 refractive cells, in which a nucleus was present, but very diffi- 

 cult to be seen, owing to the extreme fineness and apparent 

 homogeneity of the material they contained. There were also 

 several starch-grains present; and on many occasions, but on 

 one in particular, a pair of these Difflugia in zygosis, when 

 crushed in water under the slide, presented in their interior, 

 besides a great number of the three kinds of cells mentioned, a 

 still greater number of ciliated, monadic Rhizopods, of the size 

 of the bodies in the nuclear cells, and a number of small un- 

 ciliated Amoeba, about the size of the refractive cells. So far, 

 then, only, do I feel justified in stating that this appears to me 

 to be the mode in which the impregnated generation of Difflugia 

 is produced ; and if it be so, then all that remains to prove it is the 

 evidence afforded by witnessing the actual union of the ciliated 

 monadic Rhizopods with the unciliated refractive cells — an act 

 which, probably taking place within the body of D. urceolata in 

 an undisturbed condition, is not likely to be soon seen among 

 its contents when forced out of the test into water by crushing 

 and the pressure of a glass cover. 



Seeing, however, that the Diatomese and Difflugia are thus so 

 nearly allied, and that, in the former, refractive bodies different 

 from the spherical oil-globules in form, together with starch- 

 grains or vesicles, and a granular nucleus, may frequently be 

 found together in the same frustule, it does not seem to me 

 unreasonable, in the absence of more direct testimony, to infer 

 that both in the Diatomeas and, in Difflugia at least, among the 

 Rhizopoda, the mode of producing the impregnative generation 

 may be the same as that described above as the probable process 

 in the latter. 



Should this be the case, then the sarcodal cell of the spo- 

 rangial frustule of Diatomese, gaining its exit into the water in 

 its entirety, by bursting asunder the valves of its frustules sub- 



