NO. lO riiliDlNG ORGANS UK AKALllMUA — SNODGRASS 53 



besides various large insects, also crayfish, small lizards, small snakes, 

 and even small fish." 



A detailed account of observations on the feeding act of spiders 

 is given by Kastner (see Gcrhardt and Kiistner, 1937, i)p. 447-449). 

 Some species, particularly those that feed on hard-shelled insects, 

 such as beetles, merely suck out the dissolved tissues through a wound 

 in the prey. Others, including most spiders, thrust the chcliceral 

 claws into the body of the prey and tear the entrails to give the in- 

 jected digestive fluid better access to the tissues ; finally they crush 

 and knead the prey in order to get the last juice from the mangled 

 body. The digestive fluid is said by Kastner to be expelled repeatedly 

 as a large drop of clear liquid that fills the preoral cavity of the 

 spider and flows into the wound of the prey, and is then sucked back. 

 The mechanical treatment of the prey, according to Kastner, is done 

 entirely with the chclicerae, not with the jawlike lobes of the pedipalp 

 coxae. The latter serve merely as the lateral walls of the space between 

 the labrum above and the pedipalp sternum below, which is the food 

 conduit from the prey to the mouth. During feeding, Kastner ob- 

 serves, a rapid extension and contraction of the labrum within the 

 food conduit evidently exerts a preoral sucking action on the food 

 liquid. The hard, insoluble parts of the prey, prevented from entering 

 the mouth by the bristles of the coxae and sternum, accumulate in a 

 mass on the lower lip and are finally dislodged by the pedipalps. 



Earlier writers assumed the source of the exuded digestive liquid 

 to be the glands of the pedipalp coxae, or so-called "maxillary" glands, 

 but others have contended that the liquid is too copious to be produced 

 in these relatively small glands, and must come from the stomach. 

 Bertkau (1885) demonstrated experimentally that the secretion of 

 the pedipalp glands does have a solvent effect on the muscles of a fly. 

 but only after 24 hours was the muscle tissue reduced to a pulp, while 

 a live spider dissolves the tissues of a fly often in a few hours. 

 Kastner (see Gerhardt and Kastner, 1937. pp. 448-450) has shown 

 from observation on a transparent Thcridinm species that during 

 feeding there takes place a heaving and fluctuating movement of the 

 alimentary mass in the abdomen, and that when a drop of fluid is 

 discharged from the mouth the small end branches of the stomach 

 diverticula contract and expand, suggesting that by this action the 

 digestive juice is being expelled. From quantitative analyses of the 

 digestive enzymes of Aficularla. Schlottke (193O) demonstrated that 

 no proteinase of sufticient strength to accomplish extraoral digestion 

 is produced in any part of the spider anterior to the stomach. The 

 "stomach diverticula, according to Schlottke's results, secrete a strong 



