ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 319 



hatched more nearly like the adult than in Diplopods. It is more like 

 the adult than the newly-hatched IMhobius among Chilopods. " It is, 

 therefore, a highly specialised young rather than a generalised ancestral 

 form such as the hexapod larva of other Diplopoda is considered to be." 

 • It seems probable that Scutigerella is carnivorous, and it seems to 

 secrete a peritrophic membrane about the contents of its mid-gut, as do 

 some of the lower insects. 



The first joint of a typical walking leg is moved by five slender 

 muscles, which originate on the dorsal scutes. In its mode of loco- 

 motion, though not in its rate, S. immcmdata resembles the Diplopods. 

 Ecdysis seems to occur shortly before oviposition. The most common 

 method of escape from the cast skin is by freeing the head and then 

 creeping forward out of the old husk ; but this is not the only method. 



Segmentation of the Head in Diplopoda.* — Margaret Robinson 

 has examined embryos and larvae of Archispirostreptus from South 

 Africa, from which she draws certain conclusions as to the head seg- 

 ments. The embryo has two additional head -segments, the possession 

 of which would seem to give the Diplopoda a place in the Arthropod 

 system nearer to the Chilopoda and Hexapoda than that recently 

 assigned to them. These additional segments are (1) a tritocerebral 

 segment representing the tritocerebral rudiments found in Hexapoda 

 and Scolopeinlra, and also the tritocerebral segment in Crustacea ; (2) a 

 pair of rudimentary roaxillas lying in front of the pair which forms 

 the gnathochilarium in the adult. These are probably homologous 

 with the first maxillae in Chilopoda and Crustacea, and with the super- 

 linguae (Folsom) of Hexapoda. The gnathochilarium is probably a 

 part of the head, and the post-maxillary segment of Heymons and 

 Silvestri is purely a body segment. 



8. Arachnida. 



So-called Malpighian Tubes in Scorpions.f— L. Bordas has studied 

 these structures in Buthus europceus, and finds that they are inextricably 

 associated with the liver, being, in fact, excretory ducts of that organ, 

 differing in detail from the large ducts which open into the gastric 

 region. 



«. Crustacea. 



Periodic Change in Phototropism of Hermit Crabs.f — Anna 

 Drzewina finds that specimens of C'libaiiarius misanthropus Risso in an 

 aquarium show periodic changes from positive to negative phototropism, 

 which approximately synchronise with the changes of the tide. During 

 the period corresponding to neap tides the Pagurids show marked and 

 very constant negative phototropism, but as the tides become higher 

 towards the spring-tides, positive phototropism sets in. The possible 

 meaning of the parallelism is discussed, but, as the observer points out, 

 there is need for extended observations. 



* Quart. Joum. Micr. Sci., li. (1907) pp. 607-24 (1 pi., G figs.), 

 f Bull. Soc. Zool. France, xxxii. (1907) pp. 167-9. 

 X Comptes Rendus, cxlv. (1907) pp. 1208-9. 



