65 



The preliminary division of that nucleus has been constantly 

 witnessed where the phaenomena have been clearly traced. 

 In many of Ehrenberg's beautiful plates the division of the 

 nucleus is shown before that of the entire body of the mo- 

 nad has commenced ; and according to the direction of the 

 division of the nucleus, that of the monad has been either 

 longitudinal* or transverse f. Two centres of assimilative 



* See tab. 36. fig. 7. Chilodon cucullulus, 13, 14, 15. 



f Ib. 16, 17, 18. Ehrenberg calls this nucleus of the Polygastria the 

 ' testicle/ and views its division simply in the relation of the necessity of 

 each individual resulting from the general fission having such an organ : 

 meaning that each monad, developed by spontaneous fission, is perfected, 

 as regards its so-called testis, by the spontaneous division of the previous 

 testis, and not by the formation of a new one. But this is not the mode in 

 which the eye, or the circle of teeth, or the pulsating sac, is gained by 

 the second individual from the fission : the division usually takes place 

 so as to include the original organ in one or in the other moiety ; and that 

 in which it may be wanting gets the organ by a special and independent 

 development of it. The constancy of the preliminary fission of the 

 nucleus would therefore show that it related rather to the totality of the 

 act itself than to the partial completion of the individual in respect of 

 its being provided with a particular male organ of generation. How 

 then, we may inquire, does the division of the nucleus relate to the 

 performance of the general act of spontaneous fission ? Our hope of 

 any insight into this mysterious relationship would be from some light 

 to be derived by analogous phenomena. But with what phenomena 

 is the one in question analogous ? Obviously most closely with those 

 which have been observed in the successive fissions of the impregnated 

 germ-cell of those ova, such e.g. as the ova of the Strongy.lus,\)est adapted 

 to give a view of the fission analogous to those which the perseverance 

 of Ehrenberg enabled him to trace in the spontaneous fission of the 

 monad. 



The same correspondence between the successive generations of the 

 Chlamydomonas and the formation of the germ-mass in the mammalian 

 ovum has been well discerned and illustrated by Dr. Martin Barry, who 

 has observed, " On examining the figures given by Ehrenberg of successive 

 generations of the Chlamydomonas, I see a resemblance to the two, four, 

 eight, &c. groups of cells in the mammiferous ovum too striking, not to 

 suggest that the process of formation must be the same in both ; the 

 essential part of this process consisting in the division of the pellucid 

 nucleus." See my 'Lectures on Invertebrata/ p. 24, 1843. 



If this preliminary division of the germ-cell to the spontaneous fission 







