344 THE GERM-PLASM 



the seeds of yellow flowers, which resembled C. labunuim 'in 

 every character, with the exception that some of them had 

 remarkably long racemes.' 



My explanation of the fluctuation in the combination of 

 parental characters in Cytisus adaini rests on the fact that we 

 are not here concerned with the subtle diff'erences in the forces 

 which, in the reproduction of the human race, cause either the 

 maternal or the paternal idants to predominate, and which we 

 have attributed to the number of homodynamous determinants, 

 which differs according to the characters concerned : this fluct- 

 uation depends on the grosser difl"erences, and on the number 

 of idants on the two sides. Sometimes the idants of C. pur- 

 pureus^ and at others those of C. labiiniui/i. predominate in the 

 idioplasm of a cell ; and, under certain circumstances, even only 

 the one kind of idant may be represented in a cell, in which 

 case it alone will also be present in all the offspring of this cell. 



My theory is not therefore rendered less likely by the case of 

 Cytisus adanii ; we can, on the contrary, even explain the most 

 minute details of such phenomena by its means, although it was 

 not formulated for this purpose. 



6. Reversion in Parthenogenesis . 



Reproduction by means of unfertilised ova occurs regularly in 

 some plants and in many animals — more especially in crustaceans 

 and insects. We might be inclined to expect, a priori, that no 

 great degree of deviation between the mother and daughter 

 could occur at all in this monogonic form of reproduction, and 

 that at most a reversion to more remote ancestors could take 

 place. 



Such a supposition is not, however, borne out by experience. 

 A series of experiments with parthenogenetic species, which I 

 have made during the course of the last eight years, have shown 

 that although the expected uniformity between parent and oft"- 

 spring generally results in a very high degree, exceptions occur 

 occasionally, and that these must be regarded as exhibiting 

 reversions to an ancestral form many generations removed. 



The facts are briefly as follows. Two varieties of a small 

 Ostracod {Cypris repfans), possessing a very marked coloration, 

 occur in certain ponds in the neighbourhood of Freiburg. The 

 colour of one variety A, is light yellow ochre, five green spots 

 being present on either side of the shell : tlie other variety B, 



