igii.] F. H. Stkwart : Development and Anatomy of Cirripedes. 39 



(3) The Adult. 

 The anatomy of the male of Scalpellum squamuliferum. 



The shape of these animals is sufficiently indicated by pi. v, fig. i. Mounted 

 specimens measure from i mm. to 1-4 mm. in length, with a maximum horizontal 

 measurement of 7 mm. 



The outer surface is covered with hairs, which will be fully described later, 

 together with those of the hermaphrodite. 



The alimentary canal is a tube of uniformly narrow calibre. The oesophagus is 

 endowed with a sheath of circular muscular fibres. The stomach is narrow, not 

 dilated, as in the pupa. Throughout its course the canal lies dorsal to and between 

 the testes, seminal vesicles and ducti. It opens at the end of the body immediately 

 dorsal to the base of the penis. 



Nothing in the nature of food, faecal or excretory matter, was to be found in 

 any part of the intestine. The caeca, two simple epithelial tubes, arise from the 

 anterior part of the stomach and run for a short distance forward along the 

 oesophagus. 



The reproductive system consists of two simple tubular organs, uniting close to 

 their external aperture at the tip of the penis. The different regions— testes, 

 seminal vesicles and ducti — are distinguished only by the nature of their contents, 

 the wall consisting of a fine layer of endothelium throughout, except close to the 

 external aperture, where there is a sphincter. 



B. -HISTOLOGY AND DEVELOPMENT OF THE ORGANS OF THE 

 PEDUNCLE IN THE HERMAPHRODITE AND MALE. 



It will be necessary to discuss this matter in some detail since the construction 

 of the tissues, especially in the pupa, is somewhat complex, and since it is not easy 

 to follow out the development of the separate elements owing to the fact that they 

 change their appearance considerably in the successive stages. 



Darwin (5, p. 20) was the first to give an account of the development of these 

 organs, taking Lepas australis as the chief object of his study. He, however, regarded 

 the cement glands as the incipient ovaria. The true relations of the cement glands 

 and the ovaries were first defined by Krohn and Claus. 



Hoek (8) gives an excellent account of the condition of these organs in the cypris 

 of Lepas australis, with a figure which clearly distinguishes the cement apparatus, the 

 young ovaries, the yolk masses, and the vesicular spaces of the peduncle. He also 

 describes the cyprid larva of the male of Scalpellum regium, but confounds the testis 

 with a yolk mass. 



He describes the cement glands and ovaries of the adult from the study of a 

 Lepas, of Scalpellum vulgare and regium, of Conchoderma virgatum and of a Balanus. 

 Gruvel {7a, p. 448) also gives a short account of the cement glands and ovary of the 

 cyprid of Lepas australis ; he appears, however, to regard the vesicular spaces of the 



