602 ORDER APODA. 



was still more remarkable, that the matter within the gland 

 was continuous with, and differed only from, the cellular 

 matter within the ovarian tubes and caeca (from which 

 ova were in the act of formation), by being more homo- 

 geneous and more coherent. Furthermore, I have shown, 

 that in Ibla an ovarian tube, becomes by a very small 

 change, namely, by a double flexure and slight thickening 

 of its coat, converted into a gland, and thus acquires the power 

 of affecting the cellular ovarian matter and changing it 

 into cement. Now, in Proteolepas, the great ovarian sack 

 replaces the ovarian tubes and caeca ; and we here see the 

 very same relations even still more plainly ; for the coat of 

 the ovarian sack is indisputably continuous with that in- 

 vesting or forming the two cement-ducts within the two 

 threads ; and immediately that the coarse cellular matter, 

 which within the ovarian sack is being converted into ova, 

 enters the upper contracted end of the cement-duct, by 

 some power, we must suppose, inherent in its coat, it is con- 

 verted into cement, which debouches with all its usual 

 properties through the pupal antennae. I may venture to 

 reaffirm that nothing could be plainer than this structure, 

 or be in more striking conformity with my previous observa- 

 tions, given in the introduction to the Lepadidae. 



I can hardly express the perplexity which I felt when I 

 first examined Proteolepas, and when I naturally mistook 

 the mouth for the entire head, for I saw, as I thought, the 

 antennae in direct connection with the second segment of 

 the body, posteriorly to the mouth ! It was quite as mon- 

 strous and incredible an inversion of the laws of nature, as 

 those fabulous half-human monsters, with an eye seated in 

 the middle of their stomachs. After a time, I perceived 

 that the following considerations removed all difficulty, and 

 brought Proteolepas into the type of other cirripedes. 



Firstly : in ordinary cirripedes, the two cement-ducts can 

 be traced up from the cemented antennae to the glands, 

 formed by a part of the ovarian branching caeca ; and the 

 latter can be traced to where they enter, as two simple 

 tubes, the body of the animal, at a medio-dorsal point, a 



