December 31, 1909] 



SCIENCE 



971 



in size in place of the unpaired element of the 

 spermatogonia. It has been assumed that in 

 the maturation of the epgs all the chromo- 

 somes divide in both divisions, giving to each 

 matured egg a group of chromosomes similar 

 in all respects to that borne by the class of 

 spermatozoa having the idiochromosome. In 

 short, while the dimorphism of the sperma- 

 tozoa has been shown to be a fact, the similar- 

 ity of the eggs has rested upon inference only. 

 It has been assumed further that if an egg 

 is fertilized by a spermatozoon bearing the 

 idiochromosome an embryo will be produced 

 whose nuclei all have an even number of 

 chromosomes similar in all respects to the 

 oogonial groups, but if fertilized by a sperma- 

 tozoon lacking that chromosome, the resulting 

 embryonic nuclei will all have an odd number 

 of chromosomes similar to the spermatogonial 

 groups. The former class of embryos accord- 

 ingly will be females, the latter males. 



It seemed advisable to the writer to ex- 

 amine the oogenesis, fertilization and cleavage 

 of the coreid family and determine if possible 

 whether there is a basis of fact for these as- 

 sumptions. With this end in view, sections of 

 the eggs of Archivierus, Anasa, Chelinidea 

 and Protenor were made, some before laying, 

 but chiefly at intervals after laying. Al- 

 though some diificulties of technique were en- 

 countered, fairly good series were obtained. 

 The results are as follows: 



The number of oogonial chromosomes in 

 Archimerus is 16, in Aiiana 22, and in Pro- 

 tenor 14. In the first polar (oocyte) division, 

 these numbers are reduced to 8, 11 and 7, re- 

 spectively. The chromosomes exhibit the 

 same number and size relations as in the first 

 spermatocytes except that the idiochromosome 

 is here a bivalent, having resulted in all prob- 

 ability from the synapsis of two oogonial 

 chromosomes. In Protenor the idiochromo- 

 some-bivalent can be readily identified by its 

 size. In Archimerus all the chromosomes 

 divide in both polar (oocyte) divisions and it 

 is probable that the same is true for Anasa 

 and Protenor, though all stages of maturation 

 were not obtained in these two forms. As a 

 result of maturation all the eggs are of one 

 kind with regard to their chromatin-content. 



and fin-tlier the t'cmale pronucleus contains a 

 group of chromosomes similar in number and 

 size relations to that of a spermatozoon bear- 

 ing the idiochromosome. At fertilization the 

 reduced groups in the male and female pro- 

 nuclei are again distinguishable just before 

 they enter the first cleavage spindle. 



In the cleavage and early blastoderm 

 nuclei of Archimerus, Anasa, Chelinidea and 

 Protenor, the chromosomes can be readily 

 counted, and show the same numbers and size 

 relations as in the gonads, though, as a whole, 

 somewhat more elongated. Two types of 

 embryos are found, one having an odd, and 

 the other an even number of chromosomes, 

 these numbers being respectively the same as 

 occur in the spermatogonia and oogonia. 

 Accordingly, the former are males, the latter 

 females. Thus in Archimerus the embryoa 

 have either 15 or 16 chromosomes, in Anasa 

 and Chelinidea 21 or 22, in Protenor 13 or 14. 

 In short the sex of an embryo may be deter- 

 mined by counting its chromosomes. 



The results in general complete the histor.^ 

 of the idiochromosome (" accessory " chromo- 

 some) and its mate, showing their behavior in 

 the maturation of the egg and their presence, 

 either singly or together, in the embryonic 

 (somatic) nuclei. They also lend additional 

 support to the theory of chromosome-individ- 

 uality and to the recent theories of sex-pro- 

 duction based upon cytological studies. 



C. V. MORRILI. 



College of JIedicine, 

 Syracuse Umversitv 



SOCIETIES AND ACADEMIES 



THE .AMERICAN PHYSICAL SOCIETY 



The regular Thanksgiving meeting of the Phys- 

 ical Society was held in tlie new physical labora- 

 tory of the University of Illinois, Urbana, III., 

 on Saturday, Xovenilici- 27. 1009. The meeting 

 was well attended, practically all the universities 

 of the middle west, as well as several in the east, 

 being represented. President Henry Crew presided. 

 The following papers were presented: 



" Preparation and Properties of the HeusliT 

 Alloys," by A. A. Knowlton. 



" Hysteresis Tests of Heusler Alloys," by A. A. 

 Knowlton and 0. O. Clifford. 



