ZOOLOGY AND BOTANY, MICROSCOPY^ ETC. 235 



It contains a most minute comparison of the fore and hind wings of 

 a great number of different species illustrated by figures, of which it 

 is impossible to give any idea in a short abstract ; the conclusions to 

 which the author is led are, among others, that the Siricidae represent 

 the most primitive group among the Hymenoptera, since they retain 

 the embryonic character of fully developed tracheae in the wings ; an 

 immense number of details tabulated for the purposes of comparison 

 are given of the wing nervures of specimens of Apis mellifica from 

 various countries, and the varieties which they exhibit are thus 

 rendered evident. 



S. Araclmida. 



Digestive Apparatus of Spiders.* — This is the subject of an 

 elaborate paper by Dr. Bertkau, who chiefly studied Atypus piceiis. 



The transverse curved mouth-opening is bounded by an " under lip " 

 ( = a direct prolongation of the breast-plate) and an " upper lip " (for- 

 merly styled " tongue ") which is not homologous with the upper jaw of 

 Crustacea and insects. The cavity of the mouth is lined by a superior 

 and an inferior, corrugated, horny, palatal plate, each transversely 

 convex upwards. A groove traverses the upper plate and is continued 

 into the pharynx. The muscles to the pharynx serve not for altering 

 its form or volume, but merely to hold the organ firm. The pharynx, 

 piercing the central nervous system, runs sharply upwards to enlarge 

 into the horizontal, quadrilateral stomach, X-shaped in section, which 

 lies in a depression of the ento-skeleton, to which and to the sur- 

 rounding parts it is joined by muscles. So far the digestive apparatus 

 has been formed by the stomodasum. The mid-gut is characterized 

 by the formation of C£eca, which (1) in the cephalothorax are simple, 

 in three pairs (in Atypus, but more in other genera) not connected 

 together by special tissue, whilst (2) in the abdomen they are compli- 

 cated by secondary, tertiary, &c., tubes, which are boimd together by 

 connective tissue to form a compact mass. Pigment appears in the 

 intestine in the abdomen. 



In the cephalothorax lies what Plateau has compared with the 

 fat-body of Insecta, and Eay Lankester has called lacunar connective 

 tissue. In part this is glandular, according to Bertkau. 



In the abdomen the intestine runs at first along the upper con- 

 vexity beneath the dorsal vessel, and at its highest point gives off 

 on either side two pairs of ramifying c^ca which form the " chyle- 

 stomach " (formerly called " liver "), and then passes into the cloaca, a 

 posterior dilatation of the final duct of the Malpighian organs. Dr. 

 Bertkau then gives an interesting account of the histology of the 

 digestive tract and its organs, pointing out that in winter the connec- 

 tive tissue joining together the offsets of the tract with the Malpighian 

 vessels, is concerned no longer with assimilation of food, but with 

 reproduction, as is the epithelium of the caeca of the intestine. Dr. 

 Bertkau states that certain abdominal elliptical cells of this epithelium 

 go to form for the most part ova, or spermatozoa, by means of their 



* Arch. f. Mikr. Auat., xxiv. (1884) pp. 398-451 (2 pis.). 



