ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 717 



traces of the secretion. If studied by sections, the ball of the foot 

 exhibits on the upper surface some globular mucous glands imbedded 

 in the cutis, and some elongated glands, imbedded in the connective 

 tissue, on the lower side ; this is the case on the balls of all the 

 phalanges. In Rana temporaria, too, these dermal glands have a 

 similar form, only being less numerous and long ; they probably servo 

 a similar function. 



The glands in Hyla are tubular, there is a tunica propria, and the 

 cells are longish and somewhat cubical in longitudinal, but mostly 

 hexagonal in transverse section ; the nucleus, which is the only part 

 which is stained readily by picrocarmine, lies at the lower end ; the 

 cells end distally in two pointed processes. The glands do not open 

 in the annular furrow, but over the whole of the sole, especially at the 

 hinder part ; the ducts are lined by a cuticle which is shed with the 

 skin. The spongy connective tissue of the ball of the toe is filled 

 with lymph, and is thus rendered elastic, so that it adapts itself to 

 inequalities of surface ; balls of similar structure are found on the 

 tarsal joints of Orthoptera. By fastening insects feet upper- 

 most on the under side of a covering-glass which projects from a 

 glass slide, the hairs which clothe the grasping lobes of the foot may 

 be seen (e. g. in Musca erytlirocepliala) to be tipped with drops of transr 

 parent liquid. On the leg being drawn back from the glass, a 

 transparent thread is drawn out, and drops are found to be left on the 

 glass. 



The gi'asping apparatus is constructed as follows : The short grasp- 

 ing foot-hairs in Telephorus and other Coleoptera are each traversed 

 by a canal which opens at its extremity. Sundry long hairs on the 

 lower side of the tarsal joints in Telephorus are connected with nervous 

 filaments which lead from small ganglia, and thus constitute tactile 

 organs. The observation of what appear to be nerve-fibres in the 

 glands which supply the hairs with the sticky secretions is not suffi- 

 ciently certain. 



In the Orthoptera the arrangement is different : thus the tarsus of 

 a Locustid has the chitinous covering of the lower side rendered 

 very flexible by being composed of small parallel tubes, the under- 

 lying matrix is deeply plicate, and constitutes a large gland, whose 

 secretion is transmitted through the chitinous tubes and through another 

 intermediate chitinous layer to the surface. In the house-fly, the 

 grasping foot-lobes appear to be only called into play when the insect 

 has to walk on vertical smooth surfaces, for in other cases they hang 

 loosely down. So also the Echinoidea use the tube-feet only on 

 vertical surfaces. 



The use of a glutinous secretion for walking has been shown by 

 Burmeister for Dipterous larvai ; Dr. Dewitz finds the larva of a 

 Musca to use for the purpose a liquid ejected from the mouth. Thus, 

 too, the larvao of Leucojns pmncticornis accomplish their loop-liko 

 walk — the liquid in this case comes from both mouth and anus. A 

 Cecidomyia-larva is able to leap by fixing its anterior end by means 

 of a liquid of this kind. The larva of the alder-leaf beetle (Galeruca) 

 moves by drawing up its hinder end, fixing it thus, and carrying the 



