ZOOLOCxY AND BOTANY, MICROSCOPY, ETC. G45 



He discusses the literature and history of the subject, and the structure 

 of the skeleton, skin, skin-glands, and sense-organs. 



Myriopods are regarded as a phylogunetic unity, and the contrast 

 between Progoneata and Opisthogoneata is emphasised. 



5. Arachnida. 



Tracheae of Spiders.* — E. Lamy has made a detailed study of the 

 tracheal system in spiders. In Epeira, taken as type, there are four 

 tubes, invaginations of the integument, ending in tendinous extremities 

 attached in the internal tubes to the median tendons of the abdomen, 

 and in the external tubes to the dorsal integumentary insertions of the 

 fibres of the abdominal connective sac. 



In all spiders the tracheal orifices are formed by the same pair of 

 stigmata (belonging to the third abdominal segment), fused or not into 

 one, which may be displaced to the posterior end of the body. Similarly, 

 tbe tracheae — however modified — are throughout the same in origin. 

 Similar modifications seem to have occurred concurrently in different 

 families, and their degree of development does not give a clue to general 

 genetic rank, or afford a basis of classification. 



The tracheae of spiders are homologous with those of insects, and 

 also with lung- books. Both tracheae and lung-books are ectodermic 

 invaginations, elongated and ramifying in the one case, internally plaited 

 in the other. They have evolved concurrently, and illustrate in their 

 degree of development a physiological balancing. But the bulk of the 

 author's paper is taken up with a concrete description of the tracheae of 

 a long list of genera. 



Studies on the Arachnid Entosternite.t — E- 1. Pocock discusses 

 the structure of the entosternite in Xiphosurae, Scorpiones, Pedipalpi, 

 Araneae, and Solifugae, In a second chapter he discusses the homologies 

 of this difficult structure in different orders ; they seem fairly obvious 

 in the case of Pedipalpi and Araneae, and Pocock shows that they can 

 be to some extent detected over a wider range. Thirdly, the author 

 inquires into the origin of the entosternite, and finds overwhelming 

 evidence in favour of Lankester's view (1881) that it may be regarded 

 as an enlargement and interlacing of the respective tendons of the 

 muscles which are attached to it. 



Spiders of Germany.} — W. Bosenberg continues his valuable mono- 

 graph on the spiders of Germany, giving a systematic account of tbe 

 genera Theridium, Ero, Steatoda, Teutana, Enoplognatha, &c. — forty-six 

 genera in all. 



Limbless Acarid.§— I. Tragardh describes as Pimelobia apoda g. et 

 sp. n. a limbless Sarcoptid occurring under the elytra of a species of 

 beetle (Pimelia sp.) from the desert near Cairo. The parasite is very 

 degenerate, and its entire suppression of extremities is unique among 

 Acarids. All the specimens were females, fixed by the mouth to the 



* Ann. Sci. Nat. (Zoil.), pp. 148-280 (4 pis. and 71 figs.). 

 t Quart. Journ. Micr. Sci., xlvi. (1902) pp. 225-62 (2 pis.). 

 t Zoologica, xiv. (1902) pp. 97-192 (9 pis.). 

 § Zool. Anzeig., xxv. (1902) pp. 617 8 (3 rigs.). 



