414 SUMMARY OF CURRENT RESEARCHES RELATING TO 



conditions occur in the group. Thus, in the Aphoruridae, the Poduridse, 

 and the Entomobryidfe, the egg remains passive during the formation of 

 yolk, and it is the vitellogenous cells which take an active part in its 

 •elaboration. There are no ovarian follicles, and the mesodermic cells of 

 the ovary wall remain small. In the Sminthuridse somewhat similar 

 conditions obtain, but the mesodermic cells of the ovary wall take an 

 active part in yolk-formation, and are of more importance than the 

 vitellogenous cells. In Canupodea the mesodermic cells form follicles, 

 but the follicular cells are small, and the vitellogenous cells are of the 

 greatest importance in yolk-formation. In Machillis, also, follicles are 

 j>resent, but vitellogenous cells are ahsent, and the ova themselves are 

 the active agents in the elaboration of deutoplasm. The absence, or 

 slight importance, of the follicle cells, and the size and functional 

 importance of the vitellogenous cells, are interesting points of contrast 

 with the higher insects. 



Sexual Dimorphism in the Sound - producing Apparatus of 

 Orthoptera.* — A. Petrunkewitsch and G. von Guaita have studied 130 

 species (101 genera) in reference to their sound-producing organs. 

 Most Saltatoria have these organs, but they occur at diverse parts of the 

 body. Those of the females are usually different in structure from 

 those of the males. The structural dimorphism is very notable in 

 some Acridiidad and Locustidae, and the sounds are likewise very dif- 

 ferent. There is nothing to support the theory that the instruments of 

 the female have been inherited from the male side. There has been 

 independent evolution in the two sexes. 



Like Hoscker (in regard to the song of birds), the authors argue 

 that the sound-producing apparatus may be interpreted as an adaptation 

 semiring a wider range of pairing, and obviating close in-breeding. 



Stridulating Organs of Corixidse. f — G. W. Kirkaldy discusses 

 the question as to the exact organs concerned in the production of the 

 chirping noise made by the males of this family of water-bugs, and 

 concludes that they are the following. The active agent (stridulator) 

 is a comb of chitinous teeth, placed on the inner surface of the 

 thickened tarsus (pala) in the male, and absent in the female. The 

 passive agent, or stridulatory area, consists of a patch of chitinous pe^s 

 placed on the inner surface of the femur of the male ; it is absent, or 

 feebly developed, in the female. The sound is probably produced by 

 drawing the left tarsus across the right femur, and vice versa. A point 

 of interest is that the stridulating organ, in its minute details, is a 

 characteristic structure in the different species, and a means of dis- 

 tinguishing species in, at least, the male. It is possible that other parts 

 of the body are also capable of producing sounds. 



Viviparous Beetles. J — G. C. Champion and T. A. Chapman con- 

 firm the fact that viviparity occurs in the genus Orina. In 0. cacalise, 

 O. vittujera, and 0. gloriosa, the eggs develop into larvse in the ovarian 

 tubules ; in 0. tristis an egg is laid, but at an advanced stage, containing, 

 in fact, a larva with conspicuous jaws, spiracles, and eye-spots. The 



* Zool. Jahrb., xiv. (1901) pp. 291-310 (4 pis.). 



t Journ. Quek. Micr. Club, 1901, pp. 33-46 (2 pis.). 



X Trans. Entoni. Soc. London, 1901, pp. 1-1S (2 pis.). 



