i6o 



ERRANTIA. 



PART III. 



Fig. 135. Foot of a Polynoe. 



with similar sensitive organs. Fig. 135 shows the foot, 

 cirri, and bristles of a Polynoe, which are enclosed in 



plates which preserve 

 them from hurting the 

 worm. These glassy 

 bristles are beautiful 

 objects under the mi- 

 croscope ; still more so 

 are the jointed feet, 

 transparent as the 

 purest flint glass, of 

 the Phyllodoce viridis, 

 one of the most beau- 

 tiful Annelids on our 

 coasts, where it threads 



its way among young mollusca like a slender green cord, 

 exhibiting foliaceous gills in the highest perfection. 



In the marine Annelids the embryo, on leaving the 

 egg, is a gelatinous globular mass of cells furnished with 

 strong cilia. In a few hours the mass elongates and 

 divides into four parts, a head, a large ciliated segment, 

 a smaller one without cilia, and a ciliated tail. After a 

 time a succession of new segments are interposed, one 

 by one, next to the tail segment, and the correspond- 

 ing internal organs of each are developed till the worm 

 arrives at its adult state. In many Annelids the 

 embryo is highly developed within the parent ; that of 

 the Eunice has from 100 to 120 segments before it leaves 

 her ; and in the Nereis diversicolor the young, covered 

 with cilia, come out by hundreds at an orifice in the 

 side of the mother. 



Many of the marine Annelids are luminous ; electric 

 scintillations are given out during the act of nervous 

 contraction, which are increased in brilliancy and ra- 

 pidity by irritation. 



According to Professeur Quatrefages, the Annelida 



