Maech 10, 1911] 



SCIENCE 



387 



development, tlie resulting embryos do not develop 

 germ cells. This evidence strengthens the hypoth- 

 esis that these granules are really germ-cell de- 

 terminants. 



The complete paper will be published in the 

 Biological Bulletin. 



Heteroohromosomes in Mosquitoes: N. M. Ste- 

 vens, Bryn Mawr College. 



An unequal pair of heteroohromosomes is found 

 in the male germ cells of Anopheles punctipennis, 

 and the heterochromosome differentiation can be 

 seen in the resting spermatogonia and in the 

 spermatids as well as in the spermatocytes. In 

 Gulex pipiens, Ouleoo tarsalis and Theohaldia in- 

 cidens no such differentiation of heteroohromo- 

 somes is present. As the sex-determining mech- 

 anism is without doubt the same in the several 

 species of mosquitoes, it is evident that hetero- 

 chromosome differentiation is not a necessary 

 factor in the determination of sex. In Oulex and 

 Theohaldia we certainly can not say two X chro- 

 mosomes give a female and one X chromosome or 

 an X and a Y chromosome give a male, for there 

 are no X or Y chromosomes. However, it is 

 evident that, although the heterochromosome dif- 

 ferentiation may have nothing to do with sex- 

 determination, the sex-determini ig factors must 

 be closely correlated with it, and may in some 

 cases be located in the heterochromosomes. The 

 importance of a study of the origin and history 

 of the heterochromosomes apart from the idea of 

 sex-determination is urged. The complete paper 

 will be published in the Biological Bulletin. 



Origin, and Significance of Mitochondria: T. H. 



MONTQOMEET, JE., University of Pennsylvania. 



(An excerpt from a paper to be published in 

 the Journal of Morphology on the spermatogen- 

 esis of Euschistus.) 



The mitochondria undergo their chief growth 

 and multiplication in the growth period of the 

 germ cells, and are few or absent in the sperma- 

 togonia. Their mode of division in the reduction 

 mitoses is irregular, and they become divided by 

 the cell constriction. They do not arise as elim- 

 inated chromatin nor from the allosomes, but 

 apparently as a chemical interaction of nucleus 

 and idiosome. They represent part of the epi- 

 genetic history of the germ cells, and the chromo- 

 somes the preformistic. 



The Method of Cell Division in Moniezia: A. 

 RlCHAEDS, Princeton University. (Introduced 

 by Ulric Dahlgren.) 

 A reinvestigation of the development of the 



female sex products of Moniezia has not substan- 

 tiated the claim of Child that amitosis has a 

 regular place in this development. Amitotic divi- 

 sions were found at no stage in the growth of 

 these products. On the other hand, mitoses occur 

 at all stages in the development, although more 

 rarely in the early oogenesis than might have 

 been expected. Probably also periodicity of 

 mitotic divisions is one reason for the relative 

 scarcity of spindles at this stage. Cleavage divi- 

 sions are positively mitotic for the spindle in 

 each cell generation may be found. The complete 

 paper will appear in the Biological Bulletin, 



The Relation between the Formation of the Fer- 

 tilization Membra/ne and the Initiation of the 

 Development of the Echinoderm Egg: J. F. 

 McClendon, Cornell University Medical Col- 

 lege. 



Loeb observed that the sea urchin's egg may 

 develop without the formation of a fertilization 

 membrane, and I have confirmed this observation, 

 and shown that Harvey is very probably wrong in 

 his supposition that this is a case of failure in 

 " pushing out " of the membrane. Therefore I 

 concluded that " membrane formation " is not 

 essential for the segmentation of the egg, al- 

 though by furnishing protection it may insure the 

 development of the embryo. 



Loeb postulated that an osmotically active col- 

 loid exists in the unfertilized egg, but is so cov- 

 ered vrith lipoids that it does not absorb water 

 until it is squeezed out or otherwise exposed at 

 the surface of the egg, at the beginning of devel- 

 opment (when it fills the so-called " peri vitelline 

 space " ) . I have shown^ that this substance bears 

 a positive charge (is basic) since it migrates 

 toward the kathode when an electric current is 

 passed through sea water containing the fertilized 



egg. 



The unfertilized egg is imbedded in a mass of 

 jelly which is probably mucin. This jelly bears 

 a negative charge (is acid) since it combines with 

 color bases. 



When the positively charged colloid is exposed 

 at the surface and comes in contact with the 

 negatively charged jelly, the two mutually pre- 

 cipitate at their surface of contact, thus forming 

 the fertilization membrane. But if all of the 

 jelly is washed off of the egg before the latter is 

 caused to develop, no fertilization membrane is 

 formed (as I have observed) because no two oppo- 



^Am. Jour. Physiol., 1910, XXVII., 240. 



