November — December 1S83.] 



PSYCHE. 



Ill 



for a trachciil arbuscle (shrubbery) 

 whose hist ramifications are not only 

 recurved but anastomosed so as to com- 

 plete the circuit (i1 plein canal), thus 

 forming veritable arches (^anscs). His 

 figure agrees with his debcripti\"e repre- 

 sentation, showing the very numerous 

 ultimate branches of the tracheae as 

 completely arched, and his idea evi- 

 dently was that there is a capillary cir- 

 culation of air in the tracheal tubules 

 like tlie capillary circulation of blood 

 in the gills of fishes. 



Chun'- correctlv shows that the rectal 

 branchiae of Libclliila are outgrowths 

 of the [hinilj intestine, having at their 

 extremity no epithelial cells, but only 

 the intima (or cuticle) enclosing the 

 trachea! filaments. The epithelium 

 graduallv grows thinner from the base 

 towartis the extremitv of the branchial 

 laminae, and at length disappears, being 

 afterwards represented only l)y the cuti- 

 cle. The tracheae divide diclioto- 

 niouslv, finally becoming capillary air- 

 tubes, which this author also (being 

 here inaccurate) supposes to I'eunite 

 again into stronger stems. This part 

 of his plate is so confused that one 

 cannot make out whether the branches 

 reunite again or not, and we presume 

 that he did not try to follow them to 

 their extreiuities. 



In a specimen of these branchial 

 laminae which we rolled under the 

 cover-glass, we found that the multi- 

 tude of tracheal ramifications ended 



2 Chl'N, C^rl. Ueber den bau, die entwickelung und 

 physiologische bedeutung der rectaldriisen bei den 

 insekten. InauguraUdissertation. . . . Frankfurt a. M., 

 1S75. 



caecally ; all were of about the same 

 length, their extremities recurved with- 

 in the containing sac, and their tips not 

 at all swollen, but rounded otf". Thus 

 if they were stretched out they would 

 form a brusii like the hairs of a horse's 

 tail. As they are elastic and the enclos- 

 ing sac is distensible, we think it highly 

 probable that with each water-inspira- 

 tion the sacs enlarge and the tracheal 

 spray (having air forced in by the 

 forward compression of the large tra- 

 cheae) spreads out so as to bring the 

 full tide of air close to the tide of water. 

 Lton Dufour seems to have had some 

 process like this in view when he said 

 that each lamella of the branchia of 

 Potamophilns is -'probably swollen 

 during life by air transmitted by endos- 

 mosis." As we understand the case, the 

 air is injected into the l)ranchiae from the 

 rest of the body by rhythmical contrac- 

 tions, and its gases then communicate 

 endosmotically with those in the tidal 

 water, so as to secure renovation. 



The paper by N. and E. Joly on the 

 larva of Prosopistoma^ confirms our 

 observation. This larva was supposed 

 by Latreille. Dumeril and Milne-Ed- 

 wards to be a branchiopod crustacean, 

 and is so described in Milne-Edwards' 

 Histoirc dcs criistaces (v. 3, p. 558). 

 But MM. Joly found out that it w.is 

 the lar\a of a coleopterous insect,* and 

 thev figure and describe its external 



^ Jol)-, N. and E. Etudes sur le pr^tendu crustac^ au 

 sujet diiquel Latreille a cr^e le genre prosopistoma, et 

 qui n'est autre chose qii'un veritable insecte hexapnde. 

 (j\nn. des sci. nat., ZooL, 1S72, s. 5, t. 16, no. 7, p. 1-16, 

 pl- U.) 



■* It is in fact one of the epkemertdaf.. 



