352 



Mr. A. G. Bourne. 



[June 21, 



becoming larger, they acquire a narrow neck and lie in the dermic 

 layer of the skin. 



They attain a larger size among the Rhyncobdellidse than among 

 the Gnathobdellidse, becoming immense in Branchellion. 



ii. Glands which have taken up a " deep " position among or even 

 within the muscular bundles. They present three well marked 

 varieties. 



a. Salivary Glands. — These occur in all the genera, in the region of 

 the pharynx, whether that be protrusible or not. In the former case 

 they open directly into its lumen, in the latter their ducts enter into 

 its base and open along its extended lumen. When the pharynx 

 is protruded they are much stretched, when withdrawn, thrown into 

 folds. 



I@. Clitellar Glands. — These appear to occur in all the genera 

 except Clepsine, in which genus no cocoon is formed for the eggs. 

 They are exceedingly abundant. In the Rhyncobdellidse, Piscicola, 

 Pontobdella, and Branchellion they occur even far back in the body, 

 and send their ducts forward in bundles to open upon the surface of 

 the clitellum. 



7. Prostomial Glands. — The author has observed this variety in 

 Hirudo, Aulostoma, Nephelis, and Troclieta. They form clear contents 

 and send ducts forwards to open upon the prostomial region. They 

 occur all round the mouth, but in great number in the prostomium. 

 The author has not been able to determine their function. 



2. Sensory Cells. — The author has not dealt with this modification 

 of epidermic cells. Leydig has given full descriptions of these and 

 their derivatives. 



Dermis. — This lies between the epidermis and the circular muscles 

 of the body- wall. 



It consists of a matrix of connective jelly (for these and other terms 

 with regard to the connective tissues the author is indebted to a 

 paper by Professor Lankester " On the Connective and Vasifactive 

 Tissues of the Medicinal Leech"), in which are to be found the 

 various forms of connective tissue cell described below, numerous and 

 large blood-vessels, and short muscular fibres. 



The muscular fibres are not found in Clepsine, Nephelis, or 

 Troclieta. 



The lateral appendages in Branchellion are dermic developments. 

 All the connective and vasifactive elements in the dermis, form a 

 packing to the mucous glands of the epidermis. 



Muscles. 



The author describes the general arrangement of the muscles, 

 recognizing— 



Muscles of the body-wall. 



