200 ANDREWS. [Vol. VII. 



scattered over an area about 5 /a wide, corresponding in size 

 to one of the nuclei of an epidermal cell. These granules are 

 near the cuticle, the nuclei are farther in, so that the pigment 

 appears to be in the outer end of on epidermal cell, or of several 

 cells. The granules are golden yellow, yet reflect reddish light. 



The number of granules increases and the mass reflects more 

 red light ; at the same time the pigment is arranged in a com- 

 pact disk, sending a few granules deeper into the ectoblast, and 

 becoming depressed, saucer-shaped, even in a larva of twelve 

 hours. When the cell boundaries are brought out by silver 

 nitrate, the pigment appears to fill the end of a single cell. 



At twenty-one hours, when the larva is free-swimming, the 

 pigment cup is filled by a clear, refracting body or lens. 



At thirty-six hours, the somewhat pear-shaped larva swims 

 actively towards the light. It has two parts of parapodia repre- 

 sented by setae sacs, and has a conspicuous band of red pigment 

 about the prototroch. This pigment is obviously different from 

 that of the eyes, and also dissolves in alcohol, while the eye 

 pigment does not. The peculiar greenish pigment at the anal 

 end is also conspicuous at this time. 



Each eye has a lens, filling a deep cup of pigment, and reach- 

 ing out to the cuticle. In side views the cup appears as a 

 crescent. 



Similar eyes are found in N. alacris reared to this stage. 



Near each eye is a clear vesicle, in the ectoblast. 



Sections of such eyes, of one at thirty-three hours, give the 

 appearances indicated in Fig. 59 for one fifty hours old. 



At this latter period the larva has assumed the form shown 

 in Fig. 54, and the eye (Fig. 59) has an apparently semi-solid 

 lens surrounded by large pigment spherules. No cell walls 

 were seen, but the pigment seems to be in a few cells that have 

 elongated so as to bring their nuclei and the pigment next them 

 away from the cuticle into a deeper position. 



These two eyes remain in this condition for some time, as 

 shown by surface views and by sections ; but about the seven- 

 tieth hour we find them more on the ventral side, and moving 

 in from the surface, as irregular streaks of pigment enclosing a 

 clear mass. 



These streaks remain up to the one hundred and eighty-fifth 

 hour, and lie close to the above vesicles, which have become very 



