204 ANDREWS. [Vol. VII. 



The pigment begins abruptly at this line and extends inward 

 as if in one cell or between two cells ; very little is present in 

 the whole eye, perhaps no more than shown in this section. 

 The epidermal cells are not as yet marked off from the deeper 

 cells, which may become ganglion cells. 



A later stage is represented by the transverse section through 

 a posterior eye (Fig. 69). 



Several epidermal cells contain the pigment and pass out 

 through the above-mentioned curved line as clear rods extend- 

 ing towards the cuticle. In this hemispherical clear region 

 there are, however, a number of small refracting spherules or 

 minute lenses, of varying size, surrounding the largest central 

 lens. Some of these seem to lie inside the rods or cell ends. 

 Beneath the eye, towards the body cavity, there is now some 

 granular nerve substance. This stage may be compared with 

 the adult condition in Odontosyllis (Fig. 46). 



A much later stage is represented in the longitudinal section 

 (Fig. 70), which passes through one of the anterior eyes and 

 shows the entire extent of the epidermal thickening forming 

 the new head. 



The epidermis is sunk in as an oblique mass to form the eye, 

 and is separable from the underlying ganglion mass. 



The amount of pigment is much greater, though still confined 

 to a part of the optic cup. 



The bright yellow-red granules pass in irregularly as lines 

 along and apparently between the cells, but there is a sudden 

 cessation of pigment at the curved line marking off the rods. 

 These have now much the same appearance as in the adult. 



The main lens is surrounded by many very small ones, which 

 in tangential sections form a complete circle about the largest 

 central one. 



Older heads present stages of transition from that of Fig. 70 

 to the condition found in the adult sexual animal. 



Thus in the formation of eyes in the budded sexual form there 

 is the same absence of invagination as in the formation of larval 

 eyes. 



In other respects there is also fundamental agreement. In 

 the bud the process differs in that the eye is formed from more 

 numerous, larger cells, and is thus somewhat abbreviated as 

 compared with the formation in the &g% larva. 



