558 DR. L. OKLEY. 



The young are of a reddish colour, about 2 — 3 cm. in 

 length, when they leave the cocoon. They escape from the 

 free end of the egg case by the separation of the two " lips," 

 which at first, owing to their elasticity, were closed. 



Hatschek supposes a Criodrilus to lay several cocoons, 

 because the number of worms was very small in comparison 

 with the cases which he found. I placed a Criodrilus amongst 

 the roots of Slum latifolium, and in a few days found two 

 quite transparent, and therefore fresh, cocoons. It appears to 

 me, therefore, that a Criodrilus will lay two cocoons, in cor- 

 respondence with the number of the sperm ducts. It is natural 

 that more cocoons than worms should be found, since empty 

 cocoons appear throughout the year attached amongst the 

 roots ; one sometimes finds old, black, very much frayed co- 

 coons in certain places by thousands ; of freshly laid cocoons, 

 on the contrary, I have never collected more than double the 

 number relatively to the mature worms. 



Habits. — In isolated branches of large rivers, e.g. the 

 Danube, as well as in flowing streams with muddy beds, there 

 are places where the bottom is very nitrogenous owing to the 

 decomposition of organic matter. In such places there are 

 usually many aquatic plants with dense roots^ which (at any rate 

 here in Buda-Pesth, in the streams flowing into the Danube) 

 are met with in great abundance. Amongst these plants I 

 found a very large quantity of Slum latifolium, L., the 

 favourite plant of Criodrilus. 



If these plants with their roots are taken out in the spring, 

 and the '' covert " carefully examined, one finds the long 

 spindle-shaped cocoons and Criodrili engaged in egg-layings 

 so closely interlaced with the roots that they can only be 

 separated with difficulty. The egg cases are at first sight so 

 very like the Enteromorpha,that young botanists might dispute 

 as to whether they are of vegetable or animal origin. It is 

 only during the breeding season that the worms are to be 

 found amongst the roots, where copulation and egg-laying 

 takes place. After the completion of these operations they 

 return to the mud, where their genital organs commence to 



