704 



SCIENCE 



[N. S. Vol. XXIX. No. 748 



new genus (BeimarocMoa) , nine new species, 

 and to change the names (new combinations) 

 in but nineteen cases. 



Charles E. Besset 

 The Univebsity of Nebraska 



SPECIAL ARTICLES 



SECONDARY CHROMOSOME-COUPLINGS AND THE 



SEXUAL RELATIONS IN ABRAXAS 



In Professor Castle's interesting communi- 

 cation on sex-heredity, published in the issue 

 of Science for March 5, a view is advanced 

 that is akin to the " provisional formulation " 

 that I recently offered,' but seems to me a 

 decided improvement upon it. In the course 

 of his discussion Professor Castle points out 

 that the " XX and X " formula, which holds 

 true for so many insects, apparently can not 

 be applied to the conditions in Abraxas, as 

 indicated by the experimental results of Don- 

 caster and Raynor. These results only seem 

 explicable under the view that the relation 

 with which we have become familiar in other 

 insects is here reversed, the female being 

 heterozygous and the male homozygous in 

 respect to sex (Bateson, Doncaster) ; and with 

 this conclusion I concur. Definite cytological 

 evidence has now been produced that the same 

 is true of some other animals. The work of 

 Baltzer, done in Boveri's laboratory'' shows 

 that in the sea-urchin all the sperm-nuclei are 

 alike, while the egg-nuclei are of two classes, 

 approximately equal in number. All of the 

 gamete-nuclei contain 18 chromosomes. In 

 all of the sperm-nuclei and in one class of 

 egg lY of these are rod-shaped in the meta- 

 phase and anaphases of cleavage, and have a 

 terminal attachment to the spindle, while one 

 is a long chromosome that has a subterminal 

 attachment and therefore is hook-shaped. In 

 the other class of egg one of the rods is re- 

 placed by a second somewhat shorter hook- 

 shaped chromosome. The latter, therefore, 

 forms a distinctive differential between the 

 sexes; and cytologically considered the female 

 is heterozygous, the male homozygous. A 

 ' Science, January 8, 1909. 

 ' Reported by Baltzer in Verh. d. deutsch. Zool, 

 Oes., 1908, and more recently by Boveri in Sitz- 

 ungsher. d. phys.-med. Oes., Wiirzburg, 1909. 



cytological parallel to the condition inferred 

 from the experimental data in the case of 

 Abraxas is thus demonstrated. Furthermore, 

 if the differential chromosome in the sea- 

 urchin is of the same general nature as the 

 X-element of the insects, a confirmation is 

 given of Castle's assumption that in one class 

 of cases (e. g., Hemiptera) XX means the 

 female condition and X the male, while in 

 another class of cases the presence of X means 

 the female, its absence the male. 



From the point of view thus given the im- 

 portance of a cytological study of Abraxas is 

 manifest. Thanks to the courtesy of Mr. 

 Doncaster, I have for some time had this 

 material under investigation; but unfortu- 

 nately it presents great practical difficulties. 

 So much may, however, be said, that while 

 the spermatogonal divisions present a normal 

 appearance, the spermatocyte divisions, in 

 both the hybrid and the pure forms, show re- 

 markably complicated and puzzling phenom- 

 ena that are unlike anything hitherto de- 

 scribed in other insects. A detailed analysis 

 of the distribution of the chromosomes in 

 maturation will, I fear, prove impracticable, 

 and as far as this particular case is concerned 

 we are for the present reduced to mere specu- 

 lative guess-work. I think, however, that we 

 should not hesitate to guess if indications for 

 direct observation can thus be found. 



Professor Castle's assumption is that the 

 " repulsion " between the grossulariata factor 

 (" G ") and the female-producing factor 

 (" X "), postulated by Bateson, " is doubtless 

 due to the fact that the grossulariata character 

 acts as the synaptic mate to the X-element." 

 This is, perhaps, admissible; but from the 

 standpoint of the chromosome-hypothesis it 

 involves the following difficulty. In the het- 

 erozygous female (GLX in Castle's formula) 

 G is assumed to couple in synapsis, not with 

 its own homologue or allelomorph, L (as it 

 must do in the male GL or GG), but with a 

 different element, X. The L factor is thus 

 left with no synaptic mate; and this result, 

 when followed out, is foimd to involve still 

 further difficulties. Even though L be re- 

 garded as merely the absence of G, this prob- 

 ably does not mean the absence of an entire 



