194 ANCEID A. 
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. 
