ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 945 



disposition of tlie muscle-fibres of the fore-gut. A second type of " proboscis " 

 occurs in Hymenoptera, where a modification, originating as above, under- 

 goes a second turning, the primary portion remaining undifierentiated and 

 non-muscular. 



(6) The memoir concludes with a description of the so-called funnel 

 (Tricliter), beginning at the end of the fore-gut. The first and commonest 

 form arises on the outer surface of the proljoscis, near its free end, in 

 the form of a tube continuous with the chitinous layer, and extending on 

 to the anus. A somewhat divergent modification occurs in ants, wasps, 

 hornets, &c. In all cases it arises at first as a blind tube from the fore-gut. 

 It appears to grow gradually by chitinous secretion at its anterior end, and 

 to be dissolved posteriorly, passing out with the faeces. The common 

 closed form protects the mid-gut from contact with hard substances. Its 

 presence or absence, its closed or open form, depend on the nature of the 

 food. 



o. Insecta. 



Spermatogenesis.* — Prof. v. la Valette St. George adds a fifth com- 

 munication to his recent series of studies on spermatogenesis. He discusses 

 the formation of the spermatocysts in Lepidoptera, and particularly the 

 nature of the ensheathing membrane (Cystenhaut). What he long since 

 stated, he still maintains, that the membrane arises from the apposition of 

 individual cells. Recent observations have only confirmed his opinion. 

 He also noticed the frequent occurrence of processes of various length and 

 breadth arising from the membrane of the spermatocysts. The function of the 

 " cystenhaut " is to inclose, separate, and bring to contemporaneous maturity 

 its content of spermatocytes. Its role is fulfilled by other structures in 

 other cases of spermatogenesis. The author notes the increasing adoption 

 of his well-known nomenclature of spermatogenetic phases. The paper 

 contains some lively criticism of recent investigations and investigators. 



In concluding, Prof. v. la Valette St. George reiterates his classic law 

 of spermatogenesis. The mother sjierm-cells or sperraatogonia (Stam- 

 samenzellen, cellules de souche, &c., &c.), form by division an aggregate 

 of cells— the spermatogemma — which in insects, as in Amphibia, acquires 

 by the apposition of the peripheral cells a special sheath, and becomes a 

 spermatocyst (Samenschlauch). The contents of this — the spermatocytes 

 (Samenvermehrungszellen, cellules proliferatives, &c.), multiply by repeated 

 division to form the immature sperms or spermatides (Samenausbildungs- 

 zellen, &c.), from which finally the spermatozoa or spermatosomata result. 



Tannin in Insects.f — Mr. Slater communicates the results of certain 

 researches on the colours of insects. He considers that tannin, which is 

 found in some leaf- and wood-eating species, may be the cause of certain 

 of the yellow and yellowish-brown colours. Mr. Slater refers also to the 

 experiments of M. Villou, who has extracted tannin from the corn-weevil. 

 Black patterns Mr. Slater considers may be produced by the deposition of 

 iron in the parts of the chitinous tissue, which readily takes up colouring 

 matters when tannin is present. Similar lines and spots may be made to 

 appear artificially by steeping the elytra in iron solution. 



Histolog-y of Enteric Canals of Insects.J — Herr v. Faussek has dis- 

 covered that in the mid-gut of Eremobia and the larva of ^sclma, there are 

 glandular crypts, formed by special cell-complexes, in addition to the 



• Arch. f. Mikr. Anat., sxx. (1887) pp. 426-34 (1 pi.). 



t Proc. Entomol. Soc. Lond., 1887, pp. 32-4. 



: Zeitsclir. f. Wiss. Zool., xlv. (1887) pp. 694-712 (1 pi.). 



