358 



ANIMAL LIFE-HISTORIES 



LIFE-HISTORIES, &c, OF SEGMENTED WORMS 



(ANNELIDA) 



Special arrangements for protection of eggs or young do not 

 exist in the majority of the marine species of Bristle- Worms 

 (Chcetopoda), since in these, as a rule, the eggs are simply passed 

 into the surrounding water, where their chance of developing into 

 adults is exceedingly small. Sometimes, however, a mass of 

 jelly-like substance is secreted in which a batch of eggs is 

 deposited. The developing embryos are thus to some extent 

 protected, and when they hatch out the jelly serves as their 

 first food. Greenish masses of spawn of this nature, belonging 

 to some of the burrowing worms, are com- 

 monly to be seen in spring on sandy shores. 



The eggs of some Bristle- Worms are carried 

 about attached to the body of the mother, and 

 there may be special provisions for their shelter. 

 The broad flat Scale- Worms (Polynoids) possess 

 a double series of overlapping breathing-scales 

 on the upper side of the body, and in some 

 species the space underneath these structures is 

 used as a brood-pouch. In one marine worm 

 (Autolytus pro lifer, fig. 879) the female carries 

 her eggs about in a sort of bag attached to 

 the under side of the body. The wall of this 

 receptacle results from the hardening of a fluid 

 which is secreted at the time the eggs are laid. 



. && . . . 



In this particular case development is direct, 



i i i 11 r ' 1 1 



and little worms hatch out from the eggs within 

 the pouch, which resemble the adult, except in the fact that they 

 are very much shorter. 



A large number of marine Bristle -Worms may be said to 

 possess dwellings, since they live in tubes of their own manu- 

 facture (see vol. ii, p. 339), which vary greatly in shape in 

 different species, and are made up of the most diverse materials. 

 To these tubes the eggs may be attached, either to their external 

 surface, or to their inner surface, which is naturally a safer place. 

 There is an interesting specialization in one worm (Spirorbis) 

 (fig. 880) which lives in a flat spiral calcareous tube, for the 

 head of this creature bears a kind of stopper (operculum), which 



Fig. 879. A Female Bris 



t\e--w rm(Aut iytu S pro 



carrying Eggs in Pouch 



