igii.] F" H. Stewart : Development and Anatomy of Cirripedes. 47 



(3) The ADur,T Mai,e. 



The adult of the male is a pear-shaped little body, the anterior half being thicker 

 than the posterior. It measures i mm. in length, -5 in maximum breadth. 



Plate vii, fig. 5, represents a specimen slightly flattened out by mounting. The 

 antennae are in the position characteristic of the larva, and not of the ordinary adult, 

 since this form does not undergo the unfolding and straightening out which is charac- 

 teristic of the development of the ordinary adult from the pupa 



The sensory hairs are to be seen in pi. vii, fig. 5. They are supplied with nerves 

 in the same way as the hairs of 5. squamuliferum. The muscle fibres running prin- 

 cipally from the anterior to the posterior pole are clearly indicated. 



The palliai cavity and prosoma are much reduced, as in the case of 5. regium, 

 described by Hoek, but I cannot agree with this author's statement that the palliai 

 cavity is lined by a layer of condensed connective tissue — this layer is clearly a fine 

 epidermis. Neither the cavity {p.c.) nor the prosoma is clearly shown in fig. 5, but 

 they both extend through the posterior three-quarters of the body. 



The ahmentary tract is represented by a small hollow ball of cells {st.) containing 

 some cuticular and excretory matter. 



The nervous system is also much reduced. The cerebral ganglion [d.n.g.) in fig. 5 

 has been somewhat shifted from its proper place, which is on the opposite side of the 

 stomach from the reduced ventral nerve cord. 



The testis {t.) is heart-shaped; the seminal vesicles being empty were not visib.e 

 in the incompletely mature specimen from which fig, 5 was taken. The ejaculatory 

 mechanism apparently acts in the following manner. On the receipt of some stimulus 

 — very probably conveyed by the sensory hairs and passed through the reduced 

 central nervous system— the longitudinal muscles contract, the prosoma carrying the 

 ejaculatory duct is thrust through the opening of the palliai cavity, and at the same 

 time the tension m the little body is so raised that the seminal vesicles evacuate 

 themselves. 



The cement glands [c.gl.) con.sist of two or three small spherical masses of cells 

 lying posterior to the testis. Some of the cells contain the same granules as in the 

 cyprid. Two long fine ducts lead to the antennae. 



Yl.—IBLA CU3IINGII, DARWIN. 



A.— ANATOMY OF THE MALE (pi. iv, fig. 7)/ 



The body is vermiform. The prosoma is only partly marked off from the 

 peduncle. The mantle takes the form of a hollow cup, from the base and dorsal side 

 of which the prosoma arises. 



Black pigment is distributed around the mouth and on the legs. It is notewor- 

 thy that in the prosoma of the female pigment is also confined to these two regions. 



' Compare Darwin, 5, p 189. 



