I90I W. A. DAILY— RHYNCHELMIS 315 



" The Ova are now known in a large number of Oligo- 

 chseta ; but it is in Rhynchelmis that they have been most 

 thoroughly studied by Vejdovsky. 



"It is a remarkable fact that the Oligochseta can be divided 

 into two groups according to the character of their ova. 

 In the aquatic OUgochaeta the eggs are large, and contain 

 an abundance of yolk ; in the terrestrial forms the ova are 

 of microscopic size, and contain but Uttle yolk. The 

 mature egg of Rliynchelinis, which may be selected as a 

 type of a large yolked ovum, is spherical ; it has a peripheral 

 and extremely fine membrane, beneath which is a dense 

 layer of protoplasm ; connected with this is a protoplastic 

 net-work which ramifies through the entire egg, and in the 

 meshes of which are contained the yolk spherules. 



" The Cocoon : — All Oligochaeta form cocoons in which 

 the ova and the sperm are deposited, with or without 

 albumen set apart for the nourishment of the embryos. 

 The cocoon consists of a chitinous substance, and is formed 

 by the activity of the clitellum. In the cocoon of Rhyn- 

 chelmis Vejdovsky has found that there is albumen, which 

 is of course destined for the nutrition of the embryo, and 

 is transparent. 



" The cocoons of Rhynchelmis are attached to aquatic 

 plants. The process of formation being carefully watched 

 by Vejdovsky in the genus Rhynchelmis : the worm throws 

 off the cocoon over its head, crawling backwards to free 

 itself therefrom. The eggs, spermatozoa, and albumen 

 reach the interior of the cocoon as it passes over the 

 orifices of the respective ducts. Out of the numerous 

 eggs which a single cocoon originally contains, only a few, 

 sometimes only one, reaches to maturity." 



