REPORT ON THE CTRRIPEDIA. 13 



puzzled by this fact. A part of the body of this male corresponds to the peduncle of the 

 pedunculated Cirripedia, and as this is also filled up with connective tissue,— with the 

 exception of a rather narrow tubular cavity towards the rostral side, — I at first endeavoured 

 to homologize the connective tissue of the male with that of the peduncle. Extending 

 my researches also over the body of the hermaphrodite or female Scalpellum, over Lepas 

 and other genera of Cirripedia, I found that the occurrence of a well-developed mass of 

 connective tissue between the different organs within the body is the rule in all the 

 Cirripedia. In the interesting essay on the ccelom-theory by the brothers Hertwig l we 

 read that all the Arthropoda possess a very capacious body-cavity, and that in the full- 

 grown animal the intestinal tract passes freely through this cavity, a dorsal mesentery 

 uniting the intestine to the wall of the body being observed only in a younger stage of 

 the development. Whether the plurality of typical forms of Arthropoda have been 

 sufficiently investigated so as to allow of this conclusion to be drawn, I will not decide. 

 Doubtless, however, the Cirripedia have a very rudimentary body-cavity, and a well- 

 developed mass of connective tissue nearly fills up all the space left open between the 

 wall of the body and the internal organs. So the complemental males in this respect also 

 correspond in structure to the female and hermaphrodite animals. 



The internal organs consist of the well-developed genital apparatus, the nervous 

 system, the cement-glands, and the totally rudimentary and evidently functionless 

 oesophagus and stomach. 



Fig. 1 of PI. I. shows these parts in their normal position ; fig. 2 represents part 

 of these organs more strongly magnified. Testis (t), vesicula seminalis (vs), and 

 vas deferens {yd), can easily be made out in all the specimens. Neither do the other 

 organs (the nervous system, and the oesophagus with the stomach), present any further 

 difficulties after comparison with the structure of the Cypris-larva (PI. II. fig. 3). 



Digestive tract. — The oesophagus and the stomach have nearly preserved their original 

 condition ; the mouth has grown totally functionless ; its place is indicated by the 

 presence of a group of cells (PI. I. fig. 2 m), which are placed in the connective tissue 

 bordering the cavity in which the thorax is situated. The oesophagus is a narrow tube 

 which imperceptibly widens and passes over into the stomach. The latter is a pyriform 

 pouch closed on all sides, having a rudimentary intestine at the extremity opposite 

 to the cardia. It has a double wall, as can be best studied in the transverse sections 

 (PL III. figs. 6 and 7). Probably the internal wall represents a chitinous cuticle which 

 has been shed, but which could not be removed, the mouth being closed. Perhaps the 

 interna] wall represents the chitinous tube, or model of the stomach filled with excrement, 

 Darwin describes in the alimentary canal of Cirripedia. 2 In the full-grown male the 

 stomach is almost empty ; in a younger condition (PL IV. fig. 1), the stomach is filled 



1 0. and R. Hertwig, Die Coelomtheorie, Jcnaische Zeitschr., Bd. xv. p. 76, 1882. 



2 Darwin, Balanitis, p. 86, 1854. 



