CEMENTING APPARATUS. 141 



successive circular slips of cement-tissue, lying attached 

 under the circumferential slip and under the two or three 

 succeeding slips of basal membrane, an exactly analogous 

 series of changes is presented ; as indeed might have been 

 expected, as the slips of cement are absolutely continuous 

 with the contents of the ducts. Moreover, if a vertical sec- 

 tion be made across one of the last-formed slips of cement, 

 it may sometimes be seen to be apparently in the act of 

 separating into layers, with the lower layers more pulpy, 

 elastic, and white than the upper layers, which are less 

 coherent, and show as yet even still less the character of 

 cement. The cement under the circumferential and adjoin- 

 ing slips, often presents a peculiar wrinkled appearance, in 

 lines conformable with the outline of the basal membrane ; 

 but I do not believe that these are real wrinkles, though so 

 like them ; they seem to consist of sinuous threads, longer 

 or shorter, sometimes slightly branched, crossing and inter- 

 joined, and composed apparently of faintly coloured cement. 

 I suspect that these threads are formed by the union and 

 subsequent drawing out of aggregations of that matter, 

 which within the ducts is first granular, and then changes 

 into cement ; for at the orifices of the ducts these wrinkled 

 threads sweep outwards in curved lines on both sides. The 

 cement in these early stages adheres, with very little force, 

 to the basal membrane ; and with only a little more force to 

 the underlying layers of cement ; in fact, till it assumes the 

 brown translucent appearance, like solid glue, it hardly 

 seems to act as cement. 



How the cement reaches the skin of the whale, will be 

 best understood by referring to the sectional diagram 

 (PL 28, fig. 1 b). When the circumferential slip of mem- 

 brane (b) splits, a new circumferential slip will be formed 

 over it, together with new cement-glands and ducts, and 

 cement (z, z) will issue from four new orifices, and will ex- 

 tend on both sides of these orifices, till the ends meet and 

 become united, thus forming a narrow, 18-sided, con- 

 tinuous, new slip of cement, with 18 spokes proceeding 

 from it. I have not noticed lines of union in the cement 

 of any one slip ; but the matter forming each slip, certainly 

 has proceeded from four distinct orifices. Seeing how per- 



