THE ANATOMY. COCOON 147 



of a bottle-gi-een colour; one of the two specimens which I examined has three 

 bands of a darker green at one end; the shape of the cocoon was much as in the 

 Lumbricidae. In Octochaetus muUiporus and Acanthodrilus annectens the cocoon 

 has also much the same form. A considerable number of species are illustrated by 

 Vejdo-vskt; slight variations in the form can be observed in these drawings which 

 are more readily noticed than to be described. Criodrilus, on the other hand, has 

 a cocoon of a very remarkable form. It is extremely elongated and drawn out into 

 a fine filament at either end. Hoffmeistek and Benham have figured it. In 

 Benham's genus, Sparganophilus, there is a somewhat elongated cocoon, but nothing 

 like the extreme attenuation which distinguishes from that of all other Oligochaeta 

 the cocoon of Criodnlus. 



Among the aquatic Oligochaeta the cocoon is always of the same general form 

 as in the higher Oligochaeta. 



The actual deposition of the cocoon has been observed by Vejdotsry in Rhyn- 

 chdmis. There appears to be no doubt that in this worm it is formed by the 

 cUtellum, and is a product of the hypodermal glands. 



The cocoon of the Oligochaeta contains a variable amount of albuminous fluid, 

 and more or fewer eggs, from which a greater or less number of embryos arise ; the 

 sperm, too, is voided into the cocoon so that fertilization takes place here. On the 

 variations afforded by these characters d'Udekem founded (1) what is now, so 

 far as concerns these facts, known to be an erroneous classification. He divided 

 his 'Agemmes' into three families '(i) the Lombricins, (2) the Tubifex, (3) the 

 Enchytrdes.' 



In the first of these the egg is minute, there are many of them imbedded in a 

 copious albumen. In the second the egg is voluminous, there are several of them in 

 one cocoon but no albumen. In the third there is but one egg in a cocoon and no 

 albumen ; in the last two divisions the yolk in the egg performs the function of the 

 albumen. This classification has been since shown to be based upon inaccurate 

 facts ; Vejdovsky has found that in the cocoon of Ehynchelmis, which belongs to 

 the second group, there is albumen, while Michaelsen has described more than one 

 Enchytraeid in which the cocoon contains a considerable number of embryos. 



The albumen within the cocoon is, of course, destined for the nutrition of the 

 embryos ; its characters vary ; in some forms it is almost transparent and in others 

 of a milky appearance ; the latter appearance is most general among the earthworms ; 

 in RhynchdTnis and Allurus the albumen is a transparent fluid. 



The number of embryos which attain to maturity within the cocoon diff'ers 

 in different forms ; in Lumbricus rubellus there are one or two. In Octochaetus 



u 2 



