236 



SCIENCE 



[N. S. Vol. XXIX. No. 736 



Six (or more) are given ofi in the single polar 

 body, but only five are found in many of tbe 

 male eggs — others contain six (five large and 

 one small). I shaU. clear up this difficulty 

 later. 



In the spermatocytes three chromosomes 

 often appear — at other times four. There are 

 found one or two accessory chromosomes. 

 One cell gets three — or four — the other alvrays 

 two. The former produces the functional 

 sperm; the latter degenerates. 



In the second spermatocyte all the chromo- 

 somes divide equally in the functional cell. 

 The rudimentary cells do not divide, and later 

 degenerate. 



The occurrence of two kinds of males with 

 five or six chromosomes and of two kinds of 

 spermatocytes has given endless trouble and 

 has delayed publication for nearly a year. 

 The facts seem to be these. Eight, not six, is 

 the full number for this species. Two of 

 these chromosomes, one large and one small, 

 often unite. In fact these two are the two ac- 

 cessories and practically always unite to 

 produce a single accessory separating in some 

 individuals as they move into the functional 

 cell. The sexual egg contains four chromo- 

 somes. We can construct the chromosomal 

 history as follows : 



Egg 4 (3) Sperm 4 (3) 



\ / 



Stem Mother 8 (6) 



Polar body 8(6) 



Female Producer 8 (6) Male Producer 8 (6) 

 Polar body 8 (6) Polar body 8 (6) 



Female 8 (6) Male 6 (5) 



Sexual Egg 4 



Functional Sperm 4 (3) 



The most important fact brought out by 

 these results is that in the male egg a redis- 

 tribution of the eight chromosomes occurs, so 

 that the two small ones pair, and their mates, 

 the two large ones, also pair. This union 

 is evidently preparatory to the extrusion from 

 the male egg of two entire chromosomes 

 which reduces the number in the male by two. 



We catch a glimpse here of a mechanism 

 preceding the differential division of the 



chromosomes that determines the production 

 of males. 



This discovery suggests many further ques- 

 tions. I shall call attention to but one — the 

 most important. 



In both species we see that male eggs and 

 female egga are determined as such before 

 there is any loss of chromosomes. The total 

 number of chromosomes is present, yet one 

 egg is large and the other small. The pre- 

 liminaries of sex-determination for both 

 sexes go on in the presence of all the chromo- 

 somes. The male itself is produced only after 

 the elimination of two of the sex chromo- 

 somes, but the sexual female and the parthen- 

 ogenetic female are both produced in the 

 presence of all of the chromosomes. Clearly, 

 I think, the results show that changes of pro- 

 found importance may take place without 

 change in the number of chromosomes. 

 Equally clearly emerges the fact that the male 

 develops after the loss of two chromosomes. 

 This latter result shows that in the male par- 

 thenogenetic egg sex is connected with the 

 same process found in the sperm of other 

 species of insects. 



In conclusion I wish to call attention to the 

 sex ratios in the two species referred to. 



Phylloxera fallax produces its sexual forms 

 within the galls. The males and females 

 crawl out of the galls, that open to allow their 

 exit, pair, and deposit the eggs on the stems. 

 A count showed that to 1,067 female eggs 

 there were 1,049 male eggs in the galls — 

 nearly an equality in number of the sexes. 



Phylloxera carycecaulis, on the other hand, 

 produces winged forms that leave the gall 

 and fly out in the air. Those that alight on 

 the leaves of the hickory deposit their eggs on 

 the under sides of the leaves. In this species 

 a count of eggs on the leaves gave 1,316 

 male eggs and 296 female eggs, i. e., nearly 

 4.4 to 1. More important are the counts of 

 male and female producers within each gall. 

 A large number of such counts have been 

 made, of which the following give a fair idea: 

 These results show a large preponderance of 

 male producers; they also show that in some 

 cases only male producers appear and in one 



