ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 803 



5. Arachnida. 



Season Dimorphism in Spiders.* — The researclies of Weismann 

 into the phenomenon known as seasonal dimorphism among butter- 

 flies are well known ; something of the same kind is stated by Dr. F. 

 Dahl to occur in spiders. In an earlier communication this author had 

 pointed out the fact thsit Micronimata virescena and M. ornata were simply 

 two broods of the same species ; he now adduces another instance in 

 Meta segmentata and M. Mengei, stating his reasons for believing them 

 to be respectively spring and summer broods of the same species. 



Sarcoptidse.t — The first part of M. E. L. Trouessart's 'Les 

 Sarcoptides plumicoles ou Analgesines,' embraces an account of 

 Pterolichus and its allies, worked out with the aid of M. P. Megnin. 

 These mites live as commensals on the plumage of birds, feeding 

 upon the oily substance excreted by the skin, not annoying the birds 

 themselves. Several new genera and many new species are described, 

 and illustrated. About 150 species will be described, taken from 

 birds brouglit from different parts of the world. J 



6. Crustacea. 



Morphology of Crustacea.§ — Professor C. Claus discusses the 

 morphology of various parts of the Crustacean body. 



After some notes on the antennae, mandibles, and paragnaths, Dr. 

 Claus discusses the maxillse, the characters of which in the Mala- 

 costraca seem to show that that group cannot, as Hjickel and Dohrn 

 think, be derived from the Phyllopoda. He holds to his view that 

 the maxillipedes are not to be distinguished from the succeeding 

 thoracic appendages, and cites Boas as supporting him. 



Since the publication of his last essay on the Crustacea, Professor 

 Huxley has published his well-known investigation into the gills of the 

 Crustacea ; Claus, however, defers the consideration of the question 

 whether the gills have been derived from ancestral annelids, or whether 

 they are to be regarded as having been independently developed by 

 the Protostraca, contenting himself with saying that there is not yet 

 sufficient evidence to justify an answer in the direction of the former 

 view. The difference in the insertion of the gills must not be 

 supposed to be any evidence that they are morphologically different ; 

 it is probable that they were primitively all placed on the basal joint 

 of the appendages. A number of branchial formula) are given. 



After some notes on Nebalia and its relations to the Malacostraca, 

 the author passes to the significance of the Zoea and the Nauplius. If 

 the genetic relations between Annelids and Arthropods are indis- 

 putable (as the metamerism of the body, the similarity in method of 

 development of the metameres at the hinder end, the resemblance in 

 the nervous system, the segmental organs (Peripatus) and so on seem 

 to show) it follows that the stem-form of the Protostraca must have 

 been a many-jointed annelid-liko organism the extremities of which 



• Z.K.1. Anzcif,'., viii. (ISSf)) pp. 37G-7. 



t TroufBwart, E. li., ' Lch SarcoptiilcH plumifolos on AnalgcHin^s. 1* pnrtie, 

 LcH I't<;roli(h«;H (en wjllaboratiori avcc M. 1*. Megnin.),' 84 pp., 7 figs., and 2 pis,, 

 8vo, I'arifl, 1885. 



J See Amer. Natural, xix. (188.^) p. C08. 



i Arbeit. Z<K)l.-ZfK.t. Innt. Wicri, vi. nH8r)) pp. 1-108 (0 plH.). 



