Mabch 12, 1909] 



SCIENCE 



427 



A study of Oelastoeoris and the Reduviidse has 

 revealed several new types of chromosome dis- 

 tribution. 



There is present in Diplodiis and several other 

 species of the Eeduviidse a pair of idiochromo- 

 somes, which in the new types is replaced by a 

 compound group. Each of these groups as a whole 

 behaves as a pair of idiochromosomes, the small 

 idiochromosome being represented by one element 

 and the large idiochromosome by a multiple group. 

 In Fitchia the multiple group consists of two; 

 in Prionidus, three; in Oelastoeoris, four; and 

 in Acholla multispmosa (identified by E. P. 

 Van Duzee) of five chromosomes. This multiple 

 group in the second maturation division always 

 passes to one pole and the single element the 

 other, thus producing in each case two classes of 

 spermatozoa. 



The male and female chromosome groups are, 

 respectively, 27 and 28 in FitcMa; 26 and 28 in 

 Prionidus; 35 and 38 in Gelastocoris; and 26 and 

 30 in Acholla. Judging from these numerical rela- 

 tions the two classes of spermatozoa must be male 

 and female producing. 



It seems very probable that the new types have 

 arisen from the idiochromosome type by the large 

 idiochromosome breaking up into a niunber of 

 elements. 



These new types of chromosome distribution 

 offer nothing new to the theory of sex-production 

 as advocated by Wilson ('06) and Stevens ('06), 

 but they are perfectly consistent with it. 



In Acholla multispinosa, although the female 

 has the larger number of chromosomes, the male 

 seems to have the greater quantity of chromatin. 

 Sex Determination and Parthenogenesis in Phyl- 



loxerans and Aphids: T. H. Mobqan, Columbia 



University. (See Science, 1909.) 

 Maturation, Fertilization and Cleavage of Tuhu- 



laria crocea and Pennaria tiarella: Geo. T. 



Haeqitt. 



During the period between the end of the growth 

 of the egg and the formation of the polar bodies 

 the large nucleolus disappears, a concentration of 

 the chromatin occurs, the nucleus decreases in size 

 and becomes ovoid in shape. At the pointed outer 

 end only, in the nucleus of Tubularia, an aster 

 without a centrosome is usually present for a 

 considerable time. The fate of this aster is not 

 known. 



Polar bodies are formed by mitosis. No asters 

 or centrosomes are present in the first polar 

 spindle, so far the only one actually observed. 

 In Tubularia two polar bodies are formed. In the 



first polar spindle of Pennaria apparently only 

 about one half of the somatic number of chromo- 

 somes is present, though the actual number is still 

 uncertain. In Pennaria the time of formation of 

 the polar bodies varies considerably, some eggs 

 passing through this stage just before fertiliza- 

 tion, and some several hours before the liberation 

 of the eggs from the medusse. 



In Pennaria spermatozoa may enter the egg at 

 any point, though usually close to the position of 

 the egg nucleus. The transformation into the 

 sperm nucleus takes place just within the edge of 

 the egg, before migration toward the egg nucleus 

 begins. One or both of the pronuclei are often 

 multi-vesieulate, at least up to the time of con- 

 jugation. No asters or radiations of any sort are 

 present during the conjugation of the pronuclei. 



Segmentation seems to be always by mitosis and 

 cytoplasmic division is often delayed until several 

 nuclei are present. 

 Early Development of the Spider's Egg: Thos. H. 



MONTGOMEET, JR. 



The gastrulation takes place from an anterior 

 and a posterior cumulus, and from the margins 

 of the germ disc; vitellocytes form at all these 

 regions, mesoblast and entoblast only from the 

 anterior cumulus. The vitellocytes take no part 

 in producing the intestine. Entoblast develops 

 only in the abdomen. The blood cells arise from 

 the extraembryonic ectoblast, and migrate second- 

 arily into the embryo. One pair of coelomic sacs 

 develops anterior to the mouth, and the rostral 

 prominences are to be considered prestomial ap- 

 pendages of this head segment; there is no evi- 

 dence of other preoral appendages. Pulmonar/ 

 lamellse appear before the pulmonary appendages 

 invaginate, and upon these. The supraoesophageal 

 ganglion is a fusion of one pair of cerebral ridges, 

 and a pair of antero-lateral and a pair of postero- 

 lateral vesicles, all local differentiations of the 

 single head lobe. 



The Formation of the Mouth Opening and the 

 Limits of the Ectoderm and Entoderm, in the 

 Mouth of Amphibians: J. B. Johnston. 

 The Post-anal Gut and its Relation to the Doc- 

 trine of Recapitulation: Bashfoed Dean, Co- 

 lumbia University. 



It was pointed out that the general value of the 

 "biogenetic law," now often discredited, might be 

 tested by paleontological documents, even in the 

 ease of structures whose nature rendered them poor 

 subjects for f ossilization. This Dr. Dean illustrated 

 in tha case of the post-anal gut in the embryos 

 of fishes, giving reasons to show that the post- 



