34 
the centre the ends of a number of horny hair-like fibres in single series, 
or perhaps twelve or fourteen across the short diameter of the plate (ac- 
cording to the species), in shape circular, oblong, or polygonal. Outside 
these is a layer of horny matter, of nearly equal thickness, which also dips 
in between the bristles. This exterior cortical layer, like the bristles 
themselves, is fibrous in structure, and more or less colored by pigment. 
Each bristle consists of a number of concentric layers, enclosing a central 
medulla or pith made up of large cells. A section of baleen from Baleen - 
optera may be readily distinguished from one from Balcena by the larger 
size and fewness of ike hairs. As to the growth of the plates — on 
examining the base of a plate we find a flat hollow two or three inches 
deep, in which was lodged the soft pulp-blade from which the plate was 
formed. From the edge of each pulp-blade a number of soft filaments 
proceed, which become converted into the bristles, the cortical part. being 
formed from the sides of the pulp-blades. Eschnecht and Reinharclt 
(Ray Society, 1866) do not agree with Hunter and Owen (Odontography) 
that the cortex is formed from the soft gum, but rather from the sides of 
the pulp- blades. The pulp-blades of the Balcena are shorter than those of 
the Balcenoptera, although the plates formed from them are so much 
longer. According to Eschnecht and Bernhardt baleen is not formed until 
the latter half of fcetal life ; and the pulp is ten times longer in proportion 
in the new-born than in the full-grown whale. At its first formation 
bristles only are seen to project from the gum. It is clear that the central 
laminae grow much faster than those at either end, for at birth none are 
more than three or four inches long, and in the adult the middle ones are 
11 or more feet long, while the end ones have scarcely increased. This 
also applies to the subsidiary blades. Owen (Odontography) compared the 
cortex to the external cement of teeth, but even if this were correct there 
would still be nothing analogous to the enamel organ of teeth. The dis- 
covery of a number of small abortive denticles in the jaws of a fcetal i alcen- 
optera shows that baleen and teeth are not homologous, but vicarious. 
Mr. Swayne proceeded to show the similarity in structure of baleen and 
rhinoceros-horn and some other hair-structures, and viewed them all as 
" compound hair-structures." Microscopic preparations were exhibited, 
and baleen plates from three or four species of whale. 
ENTOMOLOGICAL SECTION. 
Tuesday, November 13th. — Mr. Stephen Barton, President 
of the Section, in the chair. 
The President exhibited some specimens of a minute species of 
