158 D ARCY POWER. 



On the Endothelium of the Body-Cavity and Blood-Vessels 

 of the Common Earthworm, as demonstrated hy Silver- 

 Staining. By D'Arcy Power, Exeter College, Oxford. 

 (With part of Plate X.). 

 The application to invertebrata of the methods of histological 

 research devised by students of the organization of vertebrate 

 animals, is likely to yield interesting results. At the suggestion 

 of Prof. Lankester, 1 have examined the structure of the lining 

 membranes of the body-cavity and blood-vessels of the Earth- 

 worm, by aid of the well-known method of silver-impregnation, 

 which has yielded such valuable results in connection with the 

 serous membranes and vascular structures of Vertebrata in the 

 hands of von Recklinghausen and of Klein. 



A large Earthworm, killed by chloroform, is opened along the 

 dorsal median line in a gutta-percha trough, and the body walls 

 are here and there secured to the floor of the trough by pins. 

 A one-half-per.-cent. solution of silver nitrate is then poured 

 into the trough and allowed to cover the opened worm, sufficient 

 solution being used to wash away from the exposed walls of the 

 body-cavity the white coagula formed by the liquid of the body- 

 cavity. After five minutes^ action the silver solution is poured 

 off", and an abundance of pure water substituted. Then it is 

 possible to remove with the scissors and forceps portions of the 

 membranous inter-segmental septa and complete segmental 

 organs or nephridia with their attached membranes. The wall 

 of the testicular sacs and portions of the muscular body wall 

 may also be removed for examination. The pieces cut out are 

 separately mounted in glycerine under cover-glasses in the usual 

 way, exposed to the light and then examined with the micro- 

 scope. It is necessary, if any particular organ is to be exposed 

 to the action of the silver, to so open the worm that the surface 

 of the desired organ shall be freely acted upon by the silver 

 solution, whilst at the same time it is necessary to be very care- 

 ful not to abraid the exposed surface. 



Endothelium of the Body-cavity. — Claparede (*' Histologische 

 Untersuchuiigen iiber den Regenwurm," in ' Zeitschrift fur wiss. 

 Zoologie,^ 18G9), has already described the "epithelium-like 

 clothing" of the body-cavity and the organs lying therein. In 

 particular he has figured the epithelial covering of the nerve- 

 cord — the "outer neurilemma," as he terms it, covering in the 

 longitudinal muscles and blood-vessels which surround the 

 nervous tissue, lie has also figured (Plate xlviii. fig. 5, loc. 

 cit.) certain knob-like outgrowths of the j)eritoneal coat which 

 are exactly paralleled by the knob-like outgrowths of the frog's 



