344 A. T. MASTERMAN. 



described as eyes, together with that of the reproductive organs, 

 must be left to a later paper (in which I hope to give an 

 account of the buds and young forms), but a careful examina- 

 tion has led me to believe that Cephalodiscus is provided 

 with no less than a dozen large eyes of a very primitive com- 

 pound type. 



Each plume terminates in a globular enlargement, the 

 appearance of which has been described and figured by 

 Mcintosh (3). Many of the cells of this enlargement appear 

 to contain a large clear globule of an ovoid shape. Mcintosh (3) 

 remarks, " The rugose appearance, however, is due to large 

 gland-cells containing granules and globules, which are 

 arrano'ed in a somewhat regular manner round a central 

 cavity, and which present a deep yellowish tint in the prepara- 

 tions ^' (p. !!)• I^ the parts be subjected to partial maceration 

 the clear globules can be obtained free (PI. 26, figs. 28 and 29), 

 and they remind one irresistibly of a crystalline refractive 

 lens. Two different common shapes are here indicated. In 

 lono'itudinal section of the bulb (fig. 30) it is seen that the 

 epithelium is single-layered, and consists of elongated tapering 

 cells with their nuclei mostly situated at the base. All have 

 fine pigment granules scattered throughout their interior, and 

 a wreat number of them contain the crystalline lenses referred 

 to. With Meyer's carmine and with hsematoxylin these latter 

 stain readily, one or more areas in the centre staining more 

 deeply than the rest. An axial part of the protoplasm imme- 

 diately internal to these bodies, and containing the nucleus, 

 usually appears darker than the rest of the protoplasm. The 

 lens may often be observed protruding through the cuticle to 

 the exterior, evidently an abnormal condition. 



Fi". 31 o^ives a view of one of the cells in longitudinal sec- 

 tion (unstained). It is bounded externally by a' definite but 

 fine cuticle, and its inner end tapers to a fibre-like thread, 

 which I believe to have in some cases traced into the main 

 nerve of the plume. 



The whole structure here described seems to indicate that 

 these organs are rudimentary monostichous compound eyes, 



