122 BALANIDE. 



gether. The legs, in their natural position (fig. 2), have 

 only the terminal segments of their two rami directed 

 posteriorly ; and as a consequence the spine (close to i in 

 fig. 5), borne on the penultimate segment of the outer 

 ramus, is directed in the same line with that segment and 

 with the pedicel, namely, anteriorly, and at right angles to 

 the natatory plumose spines. This short spine acts, T 

 imagine, as a defensive weapon ; it has been omitted in 

 fig. 2. Of the thorax I need not give, from my notes, any 

 more details. The abdomen (fig. 6) is similarly constructed, 

 as far as I have seen, throughout the order, with the excep- 

 tion of Alcippe (PI. 23, fig. 17), in which it is composed of 

 only one segment instead of three. In this genus the caudal 

 appendages likewise consist of only one segment, with 

 very short spines. In the pupa of Balanus balanoides, the 

 three spines borne on each caudal appendage are very much 

 more unequal in size than in the pupa of Lepas anstralis, 

 although in the latter (fig. 6) the inner spine is considerably 

 thicker than the two outer. Whether the three segments 

 of which the abdomen is composed, are the three anterior 

 or three posterior, of the normal seven segments, I know 

 not : on the view that they are the three posterior segments, 

 I presume, according to analogy, that the caudal appendages 

 are borne on the penultimate segment, and that the ultimate 

 segment is here quite aborted. 



On the internal viscera I have nothing to add. The 

 cement-duct is represented in PI. 30, fig. 2, t\ on the near 

 side, running into the antennas ; and I repeatedly traced it, for 

 the duct is very strong, as far as the disc segment ; at the 

 other end it joins the cement-gland (t) on the same side of 

 the body. This cement-gland is proved, by the clearest series 

 of facts, to be converted into the incipient ovaria and ovarian 

 caeca. The cement-glands in the older pupae could be traced 

 as far as the caeca of the stomach, exactly where the ovaria 

 lie in the mature animal ; but in some young pupae, they 

 extended further posteriorly, past the mouth, between the 

 outer and inner membranes of the overlapping carapace. 

 I have faintly shown the course of the stomach, with its two 

 caeca at the upper end ; the anus lies between the caudal 

 appendages, at the extremity (above U) of the abdomen. At 



