i 9 o8] GATES— REDUCTION IN OENOTHERA 25 



their elements were separated in the second mitosis instead of the 

 first. This view is scarcely admissible for several reasons. In the 

 first place, on this hypothesis transverse segmentation of the spirem 

 must have taken place not only between the (bivalent) chromosomes 

 but also in the middle of each chromosome, in order to give a chain 

 of fourteen bodies. Such a segmentation seems unlikely. Another 

 possible explanation would be that the chromosomes have lost their 

 identity during synapsis, and that the bodies we are dealing with now 

 are new arrangements of the chromatic material, irrespective of the 

 somatic chromosomes. Many considerations, however, strongly sup- 

 port the belief that these bodies really represent the somatic chro- 

 mosomes. The facts so far educed in Oenothera, in the opinion of 

 the writer, all favor the hypothesis of the separate existence and 

 genetic continuity of the chromosomes from one generation to another. 

 In this connection may be cited certain plants from the F t of O. lata 

 XO. gigas, which as stated elsewhere (14) have 21 chromosomes as 

 somatic number, 10 of which regularly go to one pole of the hetero- 

 typic spindle and n to the other. Occasionally, however, the segre- 

 gated numbers of chromosomes are 1 2 and 9, one chromosome having 

 gone to the wrong pole of the spindle. In this hybrid 7 of the chro- 

 mosomes are maternal and 14 paternal. If in this case there were a 

 pairing of maternal and paternal spirems, it is difficult to see how it 

 could be accomplished and result in the distribution of chromosomes 

 in the heterotypic mitosis already stated. 



It will be instructive to compare the chromosome history in this 

 cross with the often-quoted condition found by Rosenberg (23, 24) 

 in Drosera longiJoliaXD. rotundifolia. D. rotundifolia has 10 chro- 

 mosomes and D. longifolia 20, as the gametophyte number. The 

 hybrid naturally has 30 chromosomes in its sporophyte tissues, 

 but in diakinesis 20 chromosome bodies appear, 10 of which are 

 double, consisting of a larger and a smaller half, while the remaining 

 10 are the unpaired (smaller) longijolia chromosomes. The larger 

 and smaller halves of the 10 bivalents separate and pass regularly 

 to the poles of the heterotypic spindle, but the unpaired chromosomes 

 are irregularly distributed or left out of the daughter nuclei. Later 

 the pollen deteriorates. This result is strikingly different from that 

 in the Oenothera hybrid, and, while perfectly in harmony with the 



