No. 526] SEXUAL REPRODUCTION IN ANGIO SPERMS 609 



view. From a careful and extended study of mitosis in 

 spore mother-cells of higher plants, he is convinced that, 

 confirming the observations of Farmer ('05) and others, 

 there is no development of maternal and paternal 

 spirems which unite laterally to form the double chro- 

 matin thread or spirem in the mitosis under considera- 

 tion, but that the sporophytic chromosomes are arranged 

 in a lineal series in the heterotypic spirem, and that 

 consequently the two members of each bivalent chromo- 

 some are brought side by side, in case such an arrange- 

 ment is attained by the two members of each bivalent, 

 by a folding, looping or lateral approximation of parts 

 of the spirem. In his own studies the writer is unable 

 to find any justification of the doctrine that maternal 

 and paternal chromatin is represented in definitely rec- 

 ognizable lumps designated by some observers as pro- 

 chromosomes. While I can not agree with the view 

 advocated by Strasburger and Gregoire, namely, the 

 presynaptic or synaptic union of two spirems (male and 

 female), because of my personal studies, I am also un- 

 able to accept their explanation upon the ground of 

 theoretical considerations. Let us return for a moment 

 to the fusion nucleus of the fecundated egg. It is per- 

 fectly clear that, soon after nuclear fusion, paternal chro- 

 matin elements, let us say, pangens, are indistinguish- 

 able from maternal elements. These pangens, assuming 

 always the individuality of the chromosomes and of the 

 pangens, correspond in form, size and staining qualities. 

 The nucleolus or nucleoli of the egg are also similar to 

 those brought in by the sperm, in case nucleoli are 

 demonstrable in the sperm nucleus. There is nothing 

 to lead one to believe that the parental pangens do not 

 mingle in the resting nucleus (i. e., not in mitotic activ- 

 ity). If there is a pairing of homologous parts, or ex- 

 change, inter-relation, or " Wechselwirkung" of pangens, 

 or of any hereditary bearers, what reason is there* to 

 believe that such should not take place soon after fecun- 

 dation, rather than at the close of the sporophytic 

 ontogeny, or the beginning of gametophytic develop- 



