THE DEVELOPMENT OP THE EARTH-WORM. 207 



The contents of the capsules of L. trapezoides consist of 

 an albuminous mass, in which, as Rathke has demonstrated 

 in Nephelis vulgaris} two constituents are distinguishable, 

 namely, a dense, transparent, strongly refracting substance, 

 forming a kind of sponge, with very fine interstices, and a 

 liquid which fills these interstices. The albumen, under the 

 action of water, of acids, or of alcohol, assumes the appear- 

 ance of an emulsion, in consequence of the precipitation of 

 very fine granules, a decomposition which occurs during the 

 progress of development in capsules which have been left 

 intact. 



The albumen of the capsules of L. teres is colourless or 

 faintly tinged with greenish, is much more dense, and of a 

 nearly uniform aspect ; it does not dissolve, except very 

 slightly, in water or in dilute acids. 



In this jelly the eggs are scattered, and between them 

 bundles of spermatozoa. The number of the eggs in the 

 capsules of L. trapezoides is from three to eight, in those of 

 L. teres, it is from four to twenty, all of which become 

 fecundated and develop ; on the other hand, in the capsules 

 of L. trapezoides one egg only, or rarely, two or three, pro- 

 duce embryos. The other eggs not undergoing the exciting 

 influence of the male element, lose their spherical form and 

 become transformed into flat plates, with more or less irregu- 

 lar outlines ; the protoplasm, by a kind of coagulation, 

 changes into a dark substance, containing large granules, 

 and the eggs gradually dissolve and vanish without leaving 

 a trace. 



Methods of Investigation. 



I should have undertaken the study of the development of 

 L. teres more willingly than that of L. trapezoides, since in 

 the former the first stages are more simple and typical, and 

 even the later stages clearer and more distinct. Accidental 

 conditions, however, render the preparationextremely difficult. 

 The density and viscosity of the albumen, together with the 

 excessive delicacy and fragility of the embryos, make it very 

 difficult to obtain any of them uninjured. Further, as they 

 rapidly devour the whole of the albumen and store it up 

 in the digestive cavity, their body-walls becomes so tense 

 that the slightest pressure is enough to bust them. For 

 these reasons my knowledge of the development of this 

 species remains incomplete, and I shall limit myself at 

 present to the description of the development of L. tra- 



* Ratlike, Beitrage zur Eatwicklungsgeschichte der Hirudiueen, Heraus* 

 gegeben, von R. Leuckart. Leipzig, 1868, p. 3. 



