134 BALAMD.E. 



and I have there shown (singular as the fact is) that the 

 two cement-glands, with their contents, actually consist of 

 ovarian tubes with their contents (for there seemed to be a 

 relation in the state of fulness in both) in a modified con- 

 dition. In the Balanidae, I am not able, from the difficulty 

 of the dissection, to confirm these conclusions, excepting in 

 so far that the tubes on which the cement -glands are 

 formed, run into the mass of ovarian caeca; but, I may add, 

 that in the abnormal Proteolepas, belonging to another 

 Order (see the section, PI. 24, tig. 1), nothing could be 

 plainer than that the membrane of the ovarian sack [b) 

 formed the cement-ducts, and that their cellular contents, 

 which within the sack (a) were in process of conversion into 

 ova, within the ducts were converted into the cement-tissue. 

 This cement, by some unknown power, travels down the 

 ducts, and debouches at the antennae. 



In the Lepadidae, there are only two cement-glands, 

 which are situated high up in the midst of the ovarian 

 caeca, with one cement-duct proceeding from each : both the 

 glands and ducts increase in size with the age of the animal :* 

 the cement issues either permanently from the prehensile 

 antenna, or, after a short period, through apertures in the 

 peduncle, arranged irregularly or in straight lines, — the last 

 formed apertures being furthest from the central and basal 

 point of the peduncle. In the Balaninae, on the other hand, 

 at each period of growth, a pair of new cement-glands is 

 developed, larger than those last formed, and making, with 

 the older glands, a chain, connected together by what 1 

 have called the cement-trunk. The cement-trunk consists 

 of a tube, which generally becomes enlarged just before 

 entering each gland. The glands, the cement- trunk, and 

 cement-ducts, all adhere to the basal membrane or basal 

 shelly plate. Each gland gives rise to two cement-ducts, 

 these often bifurcate, and sometimes repeatedly bifurcate 

 and inosculate before pouring out their contents round the 

 circumference of the basis ; and sometimes they all first enter 

 a circumferential cement-duct. The probable cause of the 



* T had some slight reason to suspect in Pollic-ipes that new cement-glands 

 were successively formed : this is more probable in this genus than in the 

 others, inasmuch as it is the must nearly related to the Balanidae. 



