ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 581 



Oneodes and Gastrophilus are not functional, and are so greatly reduced 

 that it is difficult to homologize their parts. 



Relation of Bacteria and Yeasts to Development of Mosquito 

 "Eggs* — E. E. Atkin and A. Bacot have studied the relation between 

 the eggs and the development of the larv» of Stegomyia fasciata 

 {Aedes calopus) and the presence of bacteria and yeasts. The result 

 of the experiments on eggs is so far clear and decisive in regard to the 

 fact that the presence of bacteria, yeasts, and, less definitely, moulds, 

 does exert a stimulus causing eggs to hatch that would, apart from 

 their presence, have remained dormant for a longer period. It also 

 seems definite that this stimulus is less powerful, or may be altogether 

 ineffective, if killed cultures or sterile filtration and extracts of bacteria 

 or yeast are used. The difference is apparently one of quantity, not 

 quality, its extent being chiefly dependent upon some variation in the 

 susceptibility of the eggs. 



The larvse greedily consume both bacteria and yeasts, on which they 

 can thrive in the absence of any other food, whereas in very many 

 instances they fail entirely to develop on a variety of nutritive fluids and 

 particles, including dead bacteria, under sterile conditions. In the far 

 less numerous cases, where progress was made under apparently sterile 

 conditions, growth was always relatively very slow compared with that 

 under otherwise equivalent but unsterile conditions, and the mortahty 

 was very high. It may be said that the presence of bacteria or yeast 

 is a practical necessity for the maintaining of the species. Bacteria 

 and yeasts afford the chief food supply. The ingestion of larger 

 ' particles and the structure of the jaws need not be regarded as incom- 

 patible with this view, because such particles are likely to be covered 

 with a bacterial growth, while the jaws are of use in gnawing away 

 portions of decaying organic matter. This knowledge may be of 

 assistance in the destruction of this species of mosquito, as it should 

 enable the methods now so largely available for the purification of 

 water from bacteria to be utilized. 



New Genera of Nycteribiidse.f— Hugh Scott discusses a number 

 of points connected with these highly modified and wingless Diptera, 

 external parasites of bats, which are included in a probably polyphyletic 

 group, " Pupipara." The components differ widely among themselves, 

 but all have the characteristic of retaining the young within the body of 

 the parent till the larval life is practically completed, and of then giving 

 birth to the matured larva, which almost immediately commences its 

 transition into the pupal stage. Scott describes Eremoctenia g.n. with 

 no thoracic ctenidium. All other Nycteribiidfe have thoracic and 

 abdominal ctenidia, except Archinycterihia Speiser, which has no abdomi- 

 nal ctenidium. Another new genus is the blind Tripselia, and a new 

 subgenus Paracydopodia is erected within Cyclopodia. There is a fine 

 drawing of Eremoctenia. 



* Parasitology, ix. (1917) pp. 482-536. 

 t Parasitology, ix. (1917) pp. 593-610. 



