Miscellaneous. 423 



cephalothoracic trunks passes into the cephalothorax, where it 

 terminates in a little rounded swelling, from which issue a consider- 

 able number of small unramified tubes with thin walls. In Segestria 

 tbe trunks remain in the abdomen and do not become inflated ; but 

 they also send forth little tubes of the same nature, which, uniting 

 in two strong bundles, penetrate in great part into the cephalothorax. 

 Each posterior or abdominal trunk gives origin throughout its length 

 to a great number of little tubes going to the organs of the abdomen. 

 These tubes, starting from the trachean trunks, proceed in bundles 

 to the extremities of the appendages, gradually diminishing in size, 

 but without ramifying or presenting anastomoses. No trace of a 

 spiral thread can be detected in them, even under the strongest 

 magnifying-powers. In all the other Araneida there are in front 

 only the two anterior stigmata leading to the lungs. On the other 

 hand, we find at the posterior extremity of the body, and immediately 

 before the spinnerets, a transverse slit formed by the coalescence of 

 a pair of stigmata, and leading to two symmetrically constructed 

 tracheae. The trachean system, which is connected with these 

 stigmata, presents great differences, according to genera. In Dyctina, 

 Sund., it presents the greatest resemblance to that of By sclera, 

 Segestria, and Argyroneta, and only differs in the smaller number 

 of the tubules. In Erigone, Sav., and Micryphantes, Koch, the 

 trachean system is less developed. The air-sac, which is small, first 

 j gives origin on each side to a simple tube, which terminates in a 

 fine point. Beyond the point of origin of these two tubes the sac 

 is divided into two short, wide, and flattened trunks. From the 

 middle of their length these trunks send forth some tubules, of which 

 some remain in the abdomen, while the others pass into the cephalo- 

 thorax, where they are distributed even into the extremities. 



The genera of the family of the Attidae have a trachean system 

 constructed on a very uniform plan. It commences by two trunks 

 but little ramified, and sends forth at intervals a great number of 

 bundles of tubules. In the wall of the tubules there are seen trans- 

 verse lines which seem to indicate the appearance of a spiral thread. 



The Thomisidse have all the trachean apparatus more simplified 

 and less extended. A narrow fissure leads into a small respiratory 

 cavity, from which four branches start. The two lateral branches 

 are smaller than the intermediate ones ; but they all send forth along 

 the whole length of their course, which is limited to the abdomen, 

 branches which ramify in their turn, or terminate in a filiform point 

 without being ramified. The trachean system of the other Araneida 

 presents a still less degree of development. A narrow fissure, situ- 

 ated before the spinnerets, leads into a depressed air-cavity, at the 

 anterior extremity of which issue four simple tubes, flattened in the 

 form of ribbons, having no trace of a spiral thread, but, at most, some 

 fine granulations irregularly disseminated in their membrane. Such, 

 at least, is the general arrangement ; it presents some variations in 

 the different genera. In certain cases we see the two tubes of each 

 side, which were originally united, bifurcate further on ; or the two 

 median tubes, at first united, separate* beyond the origin of the lateral 



