ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 309 



traced. 8. Restitution takes place very slowly. Those substances 

 easily displaced are also the first to redistribute themselves. The cyto- 

 plasm seldom regains its normal position, but produces a dwarf embryo 

 outside of the yolk at the light end of the egg. 9. The age of the egg 

 determines the susceptibility to centrifugal force and the future growth 

 of the embryo. In general, an egg in a late cleavage stage becomes 

 stratified sooner than a fresh egg. Eggs centrifuged when in the blasto- 

 derm stage or older almost always produce normal embryos, and some- 

 times larvae. 10. Centrifugal force has no influence upon the rate of 

 development of eggs which produce normal embryos or larvse. 11. The 

 orientation of the embryos produced by centrifuged eggs is not affected 

 by centrifugal force. Dwarf embryos, however, are frequently formed at 

 the posterior ends of the eggs : these never produce larvas. 12. In the 

 majority of cases the eggs laid by centrifuged beetles produce normal 

 larva?. 13. The eggs of insects, although supposed by many embryo- 

 logists to be the most highly organised of any animal eggs, may have 

 their contents profoundly disturbed without preventing the production 

 of a normal embryo. The cytoplasm and nuclei of centrifuged eggs are 

 forced out of their usual positions, but often normal development takes 

 place. This would indicate that a high degree of organisation does not 

 prevent the egg from adapting itself to changed conditions. 



Minute Structure of Gut in Chrysopa perla.* — James McDunnough 

 gives a detailed histological account of the structure of the gut and its 

 associated organs (Malpighian tubules, salivary glands, etc.), both in the 

 larva and in the imago of Chrysopa perla. We shall do no more than 

 quote one of his conclusions. " The epithelium of the mesenteron is 

 formed of homomorphic cells, which have alternately the functions of 

 secretion and of absorption ; the ' Stabchensaum ' is no permanent 

 structure, but appears mainly on resting cells ; the peritrophic membrane 

 is to be regarded as a product of the whole mid-gut epithelium, and has 

 nothing in common with the intima of the stomodasuin." 



■■& 



Genital Apparatus of Neuroptera.j — H. Stitz gives a careful account 

 of this in S talis lutaria, Rhaphidia notata, Chrysopa perla, C. vulgaris, 

 Hemerobius nervosus, and MyrmeJeon. The males always show paired 

 testes, an ejaculatory duct, and a copulatory organ — the two last rela- 

 tively simple. The vesicula seminalis may be very complicated. In 

 Sialis the female parts are paired almost to the aperture, even the bursa 

 copulatris being divided. The author discusses the various forms of 

 bursa, receptaculum, vestibulum, and so on. Characteristic structures 

 are the " rosettes " on the anal valves of both sexes. 



Revision of Order Strepsiptera4 — W. Dwight Pierce has done good 

 service in preparing a revision of this interesting order, which he regards 

 as quite by itself, on a distinct line from that of Coleoptera and nearer 

 the Hymenoptera and Diptera, and as highly specialised as the highest 

 insects in any of the orders. He discusses the remarkable life-history, 



* Arch. Natur., lxxv. (1909) pp. 313-60 (5 pis.). 



t Zool. Jahrb., xxvii. (1909) pp. 377-448 (5 pis. and 26 figs.). 



% U.S. Nat. Mus., Bull. 66 (1909) pp. 1-232 (15 pis.). 



