194 ANCEIM:. 



respective animals. We have received them of a bright 

 grass-green from Mr. Loughrin, of Polperro : blue from 

 the crevices in the slate in Plymouth Sound, and have 

 dredged them of an ash-grey, as well as transparent and 

 dirty white, in five or six fathoms of water in the same 

 locality.* " The varieties of colour," observes Mr. 

 Spence Bate, " appear to be dependent upon the pro- 

 gress made in the advancement towards spawning, or in 

 some way connected with the development of the ova. 

 When the animal is blue, I have observed a double line 

 of ova traversing the length of the enlarged segment. 

 This I presume to be the ovary, or oviduct, previous 

 to the escape of the ova into the incubatory pouch, 

 which they ultimately fill to the apparent annihilation 

 of the other contents of this part of the animal. I 

 have watched specimens in a glass, and have perceived, 

 after a few days, that the blue mass, which at first 

 appeared to fill and distend the large segment of the 

 pereion, gradually diminished. It recedes first from the 

 margin ; in so doing it displays a series of layers placed 

 one before the other lying across the animal. There 

 were indications also of these layers being divided by 

 cross sections. The ova fill the pouch first, as seen in 

 fig. 6, and ultimately, as shown in fig. 8 (copied in 

 p. 177), where the embryo has considerably advanced 

 towards completion. The blue appearance is now 

 changed to brown a circumstance that is due to the 

 reddish pigment cells which mark the pereion of the 

 young animal." Thus, at a period before the animal 

 has acquired its final condition, in which the suctorial 

 structure of the mouth is entirely lost, we find the ova 

 to be present, but probably impregnation does not take 

 place until the assumption of the final state. 



* M. Hesse figures them also of a lemon colour, blood red, and sea-green. 



