502 PROF. RAY LANKESTER ON THE HEARTS OF 
But in the lower segment of the cone of Protopterus, as I have mentioned above, I 
have found minute pocket valves in the same position as the delicate “ganoid” or 
pocket valves which I discovered in Ceratodus. The position of these valves is indi- 
cated at vv in fig. 11. A magnified view of the valves is given in figure 12. They are 
so exceedingly small as to be functionally of very little, if any, significance, and may be 
regarded as evanescent organs. Just asin Ceratodus, so here do we find the under surface 
of the free margin of the longitudinal spiral valve (fig. 12, Sp v) thrown into transverse 
folds corresponding with these valves. In fact these folds must be regarded, both in Cera- 
todus and Protopterus, as indications of pocket valves arranged in transverse series on 
the concave face of the outstanding longitudinal spiral valve. Though so minute, the 
pocket valves of the conus of the Protopterus heart can be lifted with the point of a 
fine needle; and the fact that they are free in front, and attached basally, can be 
demonstrated. I did not observe chorde tendinez in connexion with these valves, I 
have as yet only examined two hearts of Protopterus annectens ; and in the better-pre- 
served specimen I found the valves as figured in fig. 12. In the second specimen I 
could not detect them, and am inclined to ascribe their absence to the inferior state of 
conservation of the heart, which was obyious enough. 
III. Heart or CHIM#RA MONSTROSA. 
The Holocephali are those fish which assuredly come nearest to the Dipnoi of all 
living forms. The resemblances in some small points are quite striking. Beyond 
the important points of identity in the structure of the skull and spiral column, 
we have:—the remarkable scissor-like teeth, closely agreeing in the two forms; 
the position of the fold of the nares in Chimera, and of the anterior and posterior 
nares in the Dipnoi; the short oval mass of intestine in both groups, really rendered 
of considerable length by the close-fitting windings of the spiral chamber within ; the 
detailed agreement of the urino-genital organs of both sexes respectively ; and, perhaps 
most strikingly, the identity in Chimera and the Protopterina of the lines of mucous 
glands disposed on the head—an agreement the closeness of which was first pointed 
out by Hyrtl. 
I am not aware that there is any detailed account of the heart of Chimera or of 
Callorhynchus extant, and I therefore turned to the examination of a specimen in my 
possession with considerable interest. The result has been disappointing, so far as the 
prospect of finding new points of agreement between Chimera and the Dipnoi is con- 
cerned. The heart of Chimera is widely separated from that of Dipnoi, is, in fact, 
eminently ichthyic and Selachian. The heart is not one of those organs with “a charmed 
life,” the characteristic structure of which remains unaffected by, indifferent to, the 
immensely important physiological changes passed through on the way from Chimera 
to Protopterus. Protopterus, with its mud-lurking habits and air-breathing capacity, 
has lost, or never developed, the Selachian limb, and has acquired a large functional 
