ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 45 



(1) when in each oviduct only one egg is formed (monoistic), which 

 is first observed in the calyx in the imago ; (2) when the eggs are 

 surrounded by a thin, soft, and non-chitinous chorion. The author 

 shows that these characters are related to the different modes of repro- 

 duction. It appears that the larvae of no other Ephemerid are so widely 

 distributed nor so numerous as those of Chloeon dipterum, in spite of 

 the smaller number of eggs in this species. This would seem to 

 indicate that here a smaller number succumb during development than 

 in oviparous species. 



Autotomy in Orthoptera.* — H. Pieron describes protective reflex 

 autotomy in Mantis religiosa, Empusa egena, GryMus campestris, Nemobius 

 silvestris, various Locustidas and Acrididre, and Forfimla auricularia. 



Excretion in Apterygota.f — Jur. Philiptschenko deals with the 

 excretory and phagocytary organ of CtenoUpisma lineata F. as a con- 

 tribution to the study of this subject. This species possesses three 

 kinds of excretory structures, viz., the urinary cells of the fat body, the 

 Malpighian vessels and pericardial cells, and a peculiar phagocytary 

 organ, the pericardial septum. In this respect this insect approaches 

 those Orthoptera which possess a permanent phagocytary organ, but 

 between the two types there is nevertheless a whole series of far-reaching 

 differences. 



&. Onychophora. 



Monograph on Onychophora.:}: — E. L. Bouvier continues his mono- 

 graphic account of the Onychophora, the present instalment beginning 

 the description of the family Peripatopsidse, which includes the three 

 sub-families Peripatoidinae, Peripatopsinas, and Paraperipatinae. 



8. Arachnida. 



Eyes of Scorpions. § — G. Police has made an elaborate study of 

 these, and denies the alleged dimorphism of the lateral and median eyes. 

 The former have been compared to simple eyes and the latter to com- 

 pound eyes. But they develop in the same way and have the same 

 essential structure. They represent a distinct type of eye. As regards 

 their development and their single lens they may be compared to ocelli, 

 but as regards the structure of the retinal elements (different from that 

 of the simple eyes of spiders, crustaceans, and insects) and the arrange- 

 ment of these, they approach the compound type. 



In the simple eyes found in most Arachnids, and in many crustaceans 

 and insects, the retinal unit is represented by a single cell, of which the 

 distal part is unpigmented. 



In the compound eyes of most crustaceans and insects, the retinal 

 unit is a group of six cells (retinule) arranged around an axis. In 

 these eyes the image, before reaching the retinule, traverses the cuticular 



* C.R. Soc. Biol. Paris, lxiii. (1907) pp. 463-5. 

 t Zeitschr. Wiss. Zool., lxxxviii. (1907) pp. 99-116 (1 pi.). 

 X Ann. Sci. Nat. (Zool.) v. (1907) pp. 61-80 (8 figs.). 

 § Zool. Jahrb., xxv. (1907) pp. 1-70 (2 pis. and 3 figs.). 



