ZOOLOGY AND BOTANY, MICKOSCOPY. ETC. G71 



Progression of Rhipidoglossidae.* — A. Robert has analysed the 

 movements of the foot in the Rhipidoglossidte in locomotion. The 

 process may be briefly described thus. Each half of the foot progresses 

 like a caterpillar. The total movement is like that of two caterpillars 

 which, instead of crawling parallel fashion by the simnltaiieous contrac- 

 tion of their homologous rings, on the contrary alternate then* con- 

 tractions. 



Morphology of Pyrula.f — Burnett Smith has made a study of some 

 of the '• morphologic changes " of the genus Pynila as observed within 

 the restricted range from the Eocene to the present day. The distinc- 

 tions l)etween the species are so slight, and they are all so unlike the 

 examples of other genera, that they may well be regarded as a single 

 genetic stock. The more important changes which have taken place 

 since the late Eocene are found not so much in the adult sculpture as in 

 the features of the apex. Without entering into details, the most 

 important points emphasized may be noted. (1) AVe may have living 

 at any one time on the earth's surface an assemblage of closely related 

 Gastropod species which differ to a marked degree in the evolutional 

 grades which they have attained. (2) In a group of closely related 

 Gastropod species, the chief modifications which are introduced with the 

 passage of time may occur mainly in the features of the early whorls, 

 while the later adult whorls may remain relatively unchanged. (3) In 

 this particular group of species, the differences in the apical characters 

 cannot be used for the division of the assemblage into separate genera^ 

 but are of use only as aids to specific discrimination, and then only when 

 the characters of the later whorls are considered together with those of 

 the apex. 



Arthropoda. 



a. Insecta. 



Maturation in Spermatogenesis of Vespa.| — E. L. Mark and M. 



Copeland describe the maturation of the spermatocyte in Vespa maculata.. 

 At one end of the cell, termed by the authors the proximal, a small bud 

 of cytoplasm containing the interzonal body (the remnants of the 

 interzonal filaments of the preceding cell-division) and the proximal 

 centrosome is protruded. For a time it remains connected with the cell 

 by a neck-like process of cytoplasm, through which may be traced extra- 

 nuclear fibres. This connecting process attenuates and breaks, and the- 

 l)ud is detached. This " Richtungskorper " consists chiefly of the 

 interzonal body, but in most cases the interzonal body is surrounded by 

 more of the unmodified cell-protoplasm than exists in the corresponding 

 globule in the honey-bee. There is evidence that the proximal centro- 

 some divides, and that the two daughter-centrosomes, in some cases at 

 least, move apart around the periphery of the globule. After the 

 formation of the non-nucleated " Richtungskorper," the cell divides and 

 two spermatids equal in size result. These are immediately meta- 

 morphosed into spermatozoa. 



* Bull. Soc. Zool. France, xxxii. (1907) pp. 55-62. 



t Proc. Acad. Nat. Sci. Philadelphia, lix. (1907) pp. 208-19 (1 pL). 



§ Proc. Amer. Acad. Arts and Sci., xliii. (1907) pp. 71-4 (8 figs.). 



