igii.] F. H. Stewart : Development and Anatomy of Cirripedes. 49 



peduncle of Ibla cumingii is also covered with hairs, but they are of a different nature 

 from those of Scalpellum, while the male is bare. 



• Genus Scalpellum. — The distribution of the hairs is bilateral ; they are parted in 

 the carinal and rostral midlines, all the hairs of each side being directed towards the 

 rostral line. They are fairly uniformly distributed, but in the male of 5. hengalense 

 there is a broad band of larger hairs on either side of the carinal midline. 



The hairs appear to be specialised outgrowths of the outermost layer of the 

 cuticle. They consist of an outer cortical portion which (in contrast with the cuticle) 

 stains intensely with iron haematoxylin and a core which does not stain. 



In the hermaphrodite of 5. squamuliferum and hengalense the hairs are large, 

 spike-like and compound. The main shaft arises from a bell-like base, which rests on 

 a papilla of cuticle. Small simple branches arise from this base from the lower 

 portion of the shaft. The base of the hairs is broader in S. hengalense than in 5. 

 squamuliferum, and the branches approximate more nearly in size to the main shaft. 



In the male of 5. squamuliferum the hairs are perfectly simple, but in that of 

 S. hengalense the larger hairs have a bifid tip. In both forms of S. gvuvelii the hairs 

 are simple, and not so rigid as in the other two species. 



The hairs in all three species are supplied with nerves (fig. 9). Fine tortuous 

 fibrils can be seen traversing the cuticle or the valves from the epiderm to the bases 

 of the hairs. These fibrils consist of a strongly staining cortex and an unstained 

 medulla. Arrived at the base of a hair the cortex becomes somewhat thickened and 

 ceases, while the medulla enters that of the hair. 



In the male of 5. hengalense I found a small ganglion in the outer wall of the 

 palliai cavity in the carinal midline (fig. 10). It consists of a single row of cells, which 

 are continuous with the epidermis, but rise slightly above the general level. A thin 

 layer of intensely staining nervous matter spreads out from the nuclei on either side 

 under the bands of larger hairs, to which I referred above. On entering the bodies of 

 the ganglion cells this nervous matter forms a series of thickened rings around the 

 nuclei. It is not clear whether the nervous matter consists of a series of fibrils or of 

 a continuous membrane-like expansion. 



The cuticle is either entirely absent or very much thinned over the ganglion. 



In the hermaphrodite of 5. squamuliferum the cuticle is invaginated inward 

 between the contiguous valves at the base of the capitulum, narrow finger-like canals 

 being formed, which are open at their outer and upper ends, and pass downwards and 

 inward through the substance of the cuticle to come in contact with the epiderm. 

 They are thickly lined with hairs and presumably are especially sensitive to vibration 

 of the water. 



Geniis Ihla. — In Ihla the hairs are stouter and more hollow. The outer layer of 

 the hair arises from the innermost layer of the cuticle, while the cortex of the hair, 

 although not cellular, is continuous with the epidermis. The entire hair thus passes 

 through the thickness of the cuticle. 



As regards the question of theory referred to on p. 34, our results {vide supra, 

 pp. 43, 44 and 48) are negative. There are no traces of female organs in the males of 



