METAMORPHOSES OF CIRRI PEDES. 129 



the caeca of the stomach, increase in size, but retain nearly 

 the same character, and thus form the two true ovaria ; their 

 middle parts become emptied of their cellular contents, and 

 are converted into the two simple ovarian tubes ; and their 

 lower ends branch out, inosculate, and form the inextricable 

 mass of ovarian tubes and caeca. The points of junction 

 on each side between the two cement-ducts and the newly 

 branched ovarian tubes, become now developed into the 

 two cement-glands. The cement-ducts, which continue 

 throughout life growing, either still enter the old antennae 

 and there pour out the cement-tissue, or they pour it out 

 through special orifices formed for this purpose in the lower 

 part of the peduncle. The changes, supervening during 

 the metamorphosis, in the ovaria and in the cemen ting- 

 apparatus, here described, I have no doubt are general 

 throughout the Order. 



I have above alluded to the primordial valves ; these are 

 beautiful objects when viewed under a high power : they 

 are composed of chitine without a trace of calcareous matter, 

 but prefigure in shape, size, and direction of growth, the 

 shelly valves soon to be formed under and round them. 

 They are composed of an outer membrane, with its mar- 

 gins separated by yellow thickened rims from the mem- 

 brane uniting the several primordial valves together; and 

 this outer membrane is underlaid by a single layer of 

 generally hexagonal, thickish cells (PI. 30, fig. 3 a), varying 

 from gS§tb of an inch in diameter. These cells seem to 

 contain a nucleus; and they are at first separated from each 

 other by clear interspaces. If a specimen be taken, only 

 a little before the formation of the calcareous valves, one 

 or more layers of membrane, marked by an hexagonal reti- 

 culation, can be separated from the lower surface of the 

 main hexagonal network. It is a singular fact, that in 

 those genera in which there are several valves, the primor- 

 dial valves occur only on five, namely, on the two scuta, 

 two terga, and the carina ; and these are the most persis- 

 tent valves in the several genera. The other valves are 

 prefigured only by brownish membrane, without the hexa- 

 gonal tissue. In the mature Lepas, the membrane con- 

 necting the several shelly valves is not moulted, but dis- 



9 



