548 SUMMARY OF CURRENT RESEARCHES RELATING TO 



the giant water-bug which occurs in great numbers in the shallow pools 

 and slowly-moving streams of Wisconsin. Nymphs and adult males, 

 which were often found with egg-clusters on their backs, were used for 

 the investigation. The spermatogonial number of chromosomes is 

 twenty-four. Only general facts were determined as to synapsis and 

 post-synaptic stages. During the post-synaptic period the double nature 

 of the chromosome threads is evident. There is a " confused " stage 

 just previous to the prophases of the first division. The "chromatoid 

 bodies " appear in this " confused " stage for the first time. Proof that 

 they originate from the cytoplasm is not lacking, because they are 

 plainly seen outside of the nuclear membrane at this stage. Tetrads 

 appear in the form of V's, rings, and rods, and all become dumb-bell 

 shaped, by continued condensation, at the time that they enter the 

 spindle. The first maturation division is an equational division. Polar 

 views show thirteen chromosomes, which is one-half the spermatogonial 

 number pJus one. The chromatoid bodies are at their maximum size in 

 this and the following division, and generally grow smaller from that 

 point onwards. The interkinesis is of short duration. No nuclear 

 vacuole is formed, the chromosomes maintaining their individuality 

 throughout. When the chromosomes arrange themselves in the meta- 

 phase of the second division an entirely new arrangement is assumed, 

 and an xy-pair of sex-chromosomes can be identified. Twelve chromo- 

 somes are delivered to each spermatid in the second division, one half 

 receiving, in addition to the eleven ordinary chromosomes, an x-chromo- 

 some, and the other half a v-chromosome. The chromatoid bodies 

 behave irregularly all along. Some spermatids have none, others have 

 one, and still others in increasing proportions have two or three. 



Eug^ster G-ynandromorph Bees.* — T, H. Morgan discusses these 

 strange forms, whose male parts are maternal, while the female parts are 

 paternal. It is suggested by Morgan that two or more spermatozoa 

 may enter the egg, one uniting with the ovum-nucleus, and the, other 

 forming an independent centre of development. Newell has shown 

 that drone bees inherit the characters of the mother. Boveri has 

 suggested, in regard to the gynandromorphs, that delayed fertilization, 

 or some irregularity in the entrance of the spermatozoon, might lead to 

 the sperm-nucleus fusing with one of the two nuclei produced by the 

 division of the &gg. A third possibility is some dislocation during 

 development of the two sex-chromosomes. 



Eggs and Early Stages of Parasitic Hymenoptera.f — F. Silvestri 

 describes the peculiarities of several types. The ova of Encyrtus mayri 

 show mono-embryonic development and have no true cyst within the 

 host. In Eiicarsia partenopea, the activity of the polar globules ends at 

 the third cleavage and involution sets in ; there is a constriction of the 

 posterior pole where the germ-cells begin to differentiate when there are 

 eight segmentation nuclei. In Prospaltella {Doloresia) co7ijugata the 



* Amer. Naturalist, 1. (1916) pp. 37-45. 



t Boll. Lab. Zool. Scuola Agric. Portici, x. (1915) pp. 66-88 (6 pis. and 4 figs.). 



