258 THE ZOOLOGIST. 



EARTHWORM STUDIES. 



By the Rev. Hikderic Friend, 



Author of 'Flowers and Flower-Lore.' 



II. OVIPOSITION AND EMBRYOLOGY. 



Our egg is not to be found in any of the famous collections 

 on which oologists have spent fortunes, and for the acquisition 

 of which museums have set apart large sums. Though no one 

 ever lavished upon it such amounts as have been paid for an egg 

 of the Great Auk or the extinct Dodo, it is practically as seldom 

 seen, and as little known, as any of the rare eggs which collectors 

 covet so ardently and prize so highly. 



We usually think of eggs as consisting of a yolk surrounded 

 by albumen, and enclosed in a hard shell made of lime or some 

 form of calcium. The eggs of birds and fowls are our types, but 

 the egg of the Earthworm has no chalk-like shell. Most eggs, 

 together with their shells, are formed within the body of the egg- 

 bearing animal, but this egg differs from the majority in this 

 respect. It is true that the egg itself is formed as usual in the 

 ovary, and passed through a tube known as the oviduct, but the 

 shell or case is fabricated by the animal externally, and is slipped 

 over the egg as it passes out of the oviduct and is about to be 

 deposited. Eggs are very commonly laid in a nest, more or less 

 elaborately constructed, and it is a rare thing for only one egg to 

 be laid during the season by each individual. It has been 

 correctly surmised that the number of eggs laid by a bird or 

 other animal bears a close relation to the exigencies and dangers 

 which the young will be likely to encounter. Hence a Pigeon 

 lays only a single pair of eggs for each brood, while the Thrush 

 deposits some half-dozen in its nest ; and Partridges, Pheasants, 

 Tits, and other birds lay from a dozen to a score. Then we find 

 that Herrings and other fish lay enormous quantities of eggs as 

 compared with many fresh-water species. 



