ZOOLOGY AND BOTANY, MICROSCOPY^ ETC. 267 



diicing a colour identical with the original " white." Ecru appeared in 

 a single male, so that it is likely that the mutation occurred in a late 

 oogonial cell, oocyte, or egg of the mother. Ivory appeared in nine 

 out of one hundred and forty-one male off-spring of a single female, 

 and mnst have occurred in an early stem cell of the ovaries of the 

 mother. The new white appeared in a single male, which had one eye 

 red and one white ; this mutation therefore occurred at a stage corres- 

 ponding to early cleavage. There is no evidence that mutations are 

 more likely to occur in gametes or germ- cells near the period of 

 maturation than in cells at any other stage in the life-cycle. The fact 

 that mosaic mutants involving recessive sex-linked genes are always 

 males indicates that mutations occur in only one member of a pair of 

 chromosomes at a time. The event which produces the mutation is, 

 therefore, exceedingly localized. The mutations of W are not quantita- 

 tive variations of the whole gene. J. A. T. 



&^ 



Saccharomycete in Dipterous Larva.^ — D. Keilin {Parasitology, 

 1920, 12, 83-91, 3 tigs.). The cavity of the body of a dipterous larva 

 {Dasyheha obscura), which usually lives in the thick brown sap filling 

 the infected wounds of elm or horse-chestnut trees, was found filled 

 with a Saccharomycete, Monosporella unicuspidata g. et sp. n. It is a 

 budding, yeast-like fungus, each cell a potential ascus, producing one 

 acicular spore. Metchnikoff's Monospora bicuspidata from Daphnia 

 magna should be referred to this new genus, and there seem to be other 

 species elsewhere, e.g. in Tylenchus as reported by Biitschli. The 

 dipterous larva, though filled with Monosporella, is still able to move, 

 but it finally dies and decomposes rapidly, thns setting free the resistant 

 forms of the parasite. • J. A. T. 



Observations on Larvae of Corethra punctipennis. — Chaxcey 

 JUDAY {Biol. Bulletin, 1921, 40, 271-86). The number of these larvte 

 in the bottom population in the deeper portions of Lake Mendota at 

 Madison, Wisconsin, is 18,000-30,000 jDer square metre. The eggs, laid 

 in the morning, sink to the bottom ; they hatched in the laboratory in 

 48 hours ; the adults emerge at night. The young larvae migrate into 

 the upper water at night as the full-grown ones do ; they remain in the 

 lower water, instead of the mud, in the daytime. The full-grown larvas 

 spend the daytime in the mud. This may be a protection from some 

 fishes, as also is the disappearance of dissolved oxygen in the hypolim- 

 nion. The live weight produced is about 300 kilograms per hectare, 

 and the dry weight about 25 kilograms. The deep-water area of the 

 lake will produce 1,318 metric tons of living larvse, or 110 metric tons 

 of dry material. Crude protein and fat constituted more than 76 p.c. 

 of the dry material. This gives these Corethra larvae a very high rank 

 as a source of food for other organisms. J. A. T. 



New African Gall-midges. — E. P. Felt {Annals Natal Museum, 

 1920, 4, 491-G). The gall-midge fauna of Africa is exceedingly in- 

 teresting and peculiar, but it is safe to state that only a very small pro- 

 portion of that fauna has come to the attention of entomologists. An 

 account is given of two new species of A'e?zA(?rm(?w//«« g. n., probably 



