40 SUMMARY OF CURRENT RESEARCHES RELATING TO 



there close to its surface, invests tlie muscles. This envelope is best 

 observed in large spiders ; in smaller species it shows no nuclei. 

 Between the muscles and the epithelium lies a thicker connective 

 tunic, from which extend septa, isolating the muscular fibres, to their 

 exterior investment. 



The secretory epithelium is monoderic. Its cells are cylindric or 

 subconical, with smooth or slightly folded sides, and a little pro- 

 longation at their fixed extremity, near which is a roimd or oval 

 nucleus. They present very striking differences, however, doubtless 

 corresponding to their states of repose or activity. In what seems its 

 state of rest, the protoplasm of the cell is mostly granular. In the 

 opposite state, a clear substance accumulates towards the free ends of 

 the cells. Such cells may appear caliciform, their free ends repre- 

 senting the duct found in unicellular glands. Dr. MacLeod dis- 

 tinguishes two other forms of secreting cells intermediate between 

 these extremes. In some spiders the depth, as well as the transverse 

 extent of the cell, varies much, giving a composite aspect to the gland 

 in transverse sections. 



The excretory duct of each poison-gland has no muscles in the 

 smaller spiders, though the two connective envelopes remain. A 

 trifling portion of the body of the gland adjoining the duct is also 

 without muscles. In the larger spiders muscles of the duct are 

 present. They display in the common house-spider a beautifully dis- 

 tinct transverse striation ; but their outer connective envelope is very 

 delicate, and has no nuclei. The epithelium is pavimental in this 

 species, cuboid or subcylindric in the common garden-spider. 



Supposed Stridulating-Organs of Steatoda guttata, Wider., and 

 Linyphia tenebricola, Wider.* — Mr. F. M. Campbell draws attention 

 to the presence, in the female of the former species, of organs similar 

 to those of the male, which were originally mentioned by Professor 

 Westring. In both sexes the apparatus consists of a strong chitinous 

 socket at the base of the abdomen, into which the hinder part of the 

 cephalothorax fits. In the male the socket is a complete ring, with 

 some spurs on the inside of its external edge, which is also roughly 

 serrated. That of the female is divided into two parts, the inferior 

 being the smallest, while the superior, as in the male, is the deepest. 

 The female has no spurs ; the inner edge, however, is undulated, and 

 at points angiilated, while a little below are stiff hairs on small pro- 

 tuberances. The chitinous thoracic extension of the male is marked 

 on its superior surface with many fine parallel transverse grooves, 

 which are absent in the female ; while in the same position on both 

 sexes are several ridges, which are less numerous in the male. 



The organs of Linyphia tenebricola are seated on the falces 

 and palpi, and are common to both sexes. On the outer side of the 

 basal joint of each falx, are about twenty parallel transverse chitinous 

 bands, placed so that their inferior edges are free. The opposing 

 surface is that of the humeral joint of each palpus, which is marked 

 with a more or less regular series of curved grooves, deep enough to 



* Journ. Linn. Soc. (Zool.). xv. (1880) pp. 152-55 (2 figs.). 



