ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 181 



hinge. The eye occurs in Mytilus, Modiola, Lithodomus, Modiolaria, 

 Septifer, Avicula, Malleus, Meleagrina, Anomia, Pinna. There are 

 usually two, one on each side, but in Anomia and Meleagrina there 

 is only one, on the left, — the upturned side. This suggests that tlu 

 eye still functions, and its absence in the abyssal Mytilid Darri/dium 

 is also noteworthy. Pelseneer finds in the peculiarity of Anomia and 

 Meleagrina, evidence of Laraarckian factors in evolution, but the 

 argument is not clear. 



Arthropoda. 

 a. Insecta. 



Vestigial Organs in Larval Muscids.* — J. Pantel notes that the 

 " troncon intermediaire " of the dorsal vessel is in reality a series of three 

 to four pairs of rudimentary cardiac chambers, and that there are rudi- 

 mentary stigmata on segments iv-xi, and dorsal communicating trachea? 

 in segments iii and xii. All these are vestigial structures. 



Pedogenesis of Cecidomyids.t — W. Kahle has studied the develop- 

 ment of the proliferating Miastor-\a,rv9d. It is genuine parthenogenesis. 

 There is only one maturation-division, and it is an equation-division. 

 The polar body divides into two, which show the beginnings of another 

 mitosis. At the 8-cell stage there is a definite separation of soma and 

 germ-lineage, the latter being started by the cell at the posterior pole. 

 Its " polar plasm " is preformed in the immature ovum. In the 4-cell 

 stage there is a diminution-process in the three somatic nuclei, and it 

 goes on in the seven somatic nuclei of the next stage. There is a 

 halving of the chromosomes ; in the germ-cell lineage there are 20-24, 

 in the reduced nuclei there are 10-11. The blastoderm is established at 

 the 58-cell stage, and 8 " urogonia " or primitive germ-cells lie at the hind 

 end of the blastoderm. Yolk-cells are formed by immigration from the 

 blastoderm. The eight urogonia come to lie in the eleventh segment, 

 where they multiply to form the ovary. The nutritive cells of the 

 ovarian follicles come from the mesoderm. In the dorsally curved 

 germinal streak stage there are hints of coelom-sacs. The mid-gut is 

 formed from the proximal ends of the fore-gut and hind-gut. 



Froth in Spittle-Insects.ij: — Braxtou H. Guilbeau has made a careful 

 study of the formation of the froth in Aphrophora parallela, Lepyronia 

 quadr annularis, and Glastoptera proteus, and finds that the secretion is 

 made up from two sources. The fluid portion is the anal secretion 

 into which the insect, by means of its caudal appendages, introduces 

 numerous air-bubbles. The glands of Batelli, situated in the pleural 

 region of the seventh and eighth abdominal somites, secrete a mucila- 

 ginous substance which, added to the anal fluid, renders it viscous and 

 thus causes the retention of the air-bubbles. The so-called branchial 

 appendages of Morse and of Porta are merely plates of this mucila- 

 ginous secretion. 



• Comptes Rendus, cxlviii. (1909) pp. 107-10 (1 fig.). 

 t Zoologica, Iv. (1908) pp. 1-80 (6 pis. and 38 figs.). 

 X Amer. Nat., xlii. (1908) pp. 783-98 (8 figs.). 



