ATTACHMENT. 35 



the multiple external coats of the gland and ovarian tubes 

 could be seen to be continuous. The cellular contents of 

 the tubes passed into the more opaque cellular contents of 

 the gland, by a layer of transparent, pulpy, pale, yellowish 

 substance. There appeared in several instances to be a 

 relation, between the state of fulness and condition of the 

 contents of the gland, and of the immediately adjoining 

 portions of the ovarian tubes. In one specimen of 

 Pollicipes mitella it was clear that the altered, tough, 

 yellow, transparent, non-cellular contents of the two 

 glands and ducts, had actually invaded for some little 

 distance, the two ovarian tubes which ran into them, thus 

 showing the continuity of the whole. From these facts I 

 conclude, without hesitation, that the gland itself is a part 

 of an ovarian tube specially modified ; and further, that 

 the cellular matter, which in the ovarian tubes serves for 

 the development of the ova, is, by the special action of the 

 walls of the gland, changed into the opaquer cellular matter 

 in the ducts, and this again subsequently into that tissue 

 or substance, which cements the Cirripede to its surface 

 of attachment. 



As the individuals grow and increase in size, so do the 

 glands and cement-ducts ; but it seems often to happen, 

 that when a specimen is immovably attached, the 

 cementing apparatus ceases to act, and the cellular con- 

 tents of the duct become converted into a thread of 

 transparent tough cement ; the investing membrane, also, 

 of the ducts, in Conchoderma sometimes becomes hard 

 and mamillated. I have already alluded to the case of 

 a Pollicipes, in which both glands and ducts, and even 

 a small portion of the two adjoining ovarian tubes, had 

 become thus filled up. As in sessile Cirripedes, at every 

 fresh period of growth a new cement gland is formed, it 

 has occurred to me, that possibly in Pollicipes something 

 similar may take place. In sessile Cirripedes, the old 

 cement-glands are all preserved in a functionless condi- 

 tion, adhering to the membranous or calcareous basis, 

 each new larger one attached to that last formed, and 



