ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 617 



to the mainland. The cause remains unknown. The bees become 

 disinclined to work, they lose their power of flight, they crawl about the 

 ground. The abdomen swells, wings and legs are affected. The 

 foragers are always the first affected. Finally the whole colony of 

 workers is found massed together in front of the hive or on the ground, 

 except a few which are found crowded round the queen. The mysterious 

 disease may be distinguished from Bee Paralysis, "May Pest," and 

 Dysentery. 



Spermatogenesis of Stenobothrus viridulus.* — C. F. U. Meek 

 finds that the chromosomes of the spermatogonial complex can be 

 arranged in a graduated series of pairs, and are divisible into three 

 groups, viz., large, small, and medium-sized chromosomes. The number 

 is constant and is seventeen, the fourth largest being unpaired and 

 corresponding with the " monosome " and " accessory " chromosome of 

 other writers. All the members of the spermatogonial complex divide 

 in mitosis ; but the odd or heterotopic chromosome often " lags," and 

 can be seen on the spindle when the ordinary chromosomes are 

 assembling at the poles. 



The ordinary chromosomes divide in the primary spermatocyte 

 metaphase, and their halves pass to opposite poles of the spindle ; the 

 heterotopic chromosome shows no sign of division, and passes entire to 

 one daughter-cell, while the ordinary chromosomes are still on the 

 equatorial plate. In this manner dimorphism of the subsequent 

 spermatozoa is effected. 



The author has been unable to discover whether reduction — the 

 separation of conjugant members — occurs at the first maturation division 

 or the next ; possibly both divisions are equational, and only a numerical 

 reduction takes place as a result of lateral association of chromatin 

 granules or masses on the reticulum threads prior to the primary 

 spermatocyte prophase of mitosis. 



The secondary spermatocytes show seven or eight chromosomes, 

 and this difference is due to the presence or absence of the heterotropic 

 chromosome. In the spermatids the heterotropic chromosome undergoes 

 resolution into particles, whose identity is indistinguishable in the 

 common chromatin mass. 



Though the individuality of the chromosomes is quite lost in the 

 resting-stages, there is strong reason for supposing that the same 

 elements appear on the successive mitotic spindles throughout de- 

 velopment. It must not be assumed, however, that corresponding 

 chromosomes of two successive metaphases contain the same individual 

 chromomeres. 



New Flea from South Africa.j — J. Waterston describes Xenopsylla 

 trispinis sp. n., evidently close to X. cheopis Rothsch. and A', nubieus 

 Rothsch., taken from nests of the cliff swallow (Petrochelidon spilodera), 

 also from the birds themselves, and on the walls of the building (in 

 Cape Colony) where the birds nested. 



* Journ. Linn. Soc. (Zool.) xxxii. (1911) pp. 1-21 (3 pis.). 



t Proc. R. Phys. Soc. Edinburgh, xviii. (19 LI) pp. 192-5 (6 figs.). 



