248 
PEOGRESS OF MICROSCOPICAL SCIENCE. 
had the opportunity of examining the dark, granular masses found in 
the one kind, has failed to satisfy himself that this substance is 
plentifully penetrated by mycelial threads — although, even in this 
variety, the tissues immediately adjoining the excavated channels 
containing the debris present no trace of a mould. Nor, on the other 
hand, are we aware that any observer has confirmed the statement 
that precisely similar vegetations are to be found in the roe-like 
particles of the ' pale ' variety : on the contrary, quite an array of 
authorities might be referred to who have emphatically declared that 
no such appearances can be detected. Until this discrepancy can be 
definitely settled, the doctrine that the disease is due to any such 
vegetable parasite is quite untenable; and even were such growths 
indubitably demonstrated to exist in both kinds, it would still have to 
be shown that Godfrey was wrong in inferring, as he appears to have 
done some thirty years ago, that the peculiar substance was ' an 
accidental product in, but not forming part of, this peculiar disease 
of the foot.' " 
Structure and Development of the Teeth in Ophidia. — A very valu- 
able paper was lately read before the Eoyal Society by Mr. C. S. 
Tomes, M.A., on the above subject. The following is an abstract 
from the ' Proceedings of the Eoyal Society,' No. 157. " Contrary to 
the opinion expressed by Professor Owen and endorsed by Giebel and 
all subsequent writers, the author finds that there is no cementum 
upon the teeth of snakes, the tissue which has been so named proving, 
both from a study of its physical characters and, yet more conclusively, 
from its development, to be enamel. The generalization that the 
teeth of all reptiles consist of dentine and cement, to which is 
occasionally added enamel, must hence be abandoned. Without as 
yet pledging himself to the following opinion, the author believes 
that in the class of Eeptiles the presence of cementum will be found 
associated with the implantation of the teeth in more or less complete 
sockets, as in the Crocodiles and Ichthyosaurs. The tooth-germs 
of Ophidia consist of a conical dentine-germ, resembling in all 
save its shape that of other animals, of an enamel organ, and of a 
feebly expressed capsule, derived mainly from the condensation of the 
surrounding connective tissue. The enamel organ consists only of a 
layer of enamel-cells, forming a very regular columnar epithelium, 
and of a few compressed cells external to this, hardly amounting to a 
distinct layer ; the enamel organ is coextensive with the dentine- 
germ. There is no stellate reticulum separating the outer and inner 
epithelia of the enamel organ. The successional teeth are very 
numerous, no less than seven being often seen in a single section ; 
and their arrangement is peculiar, and quite characteristic of the 
Ophidia. The tooth next in order of succession is to be found at the 
inner side of the base of the tooth in place, where it lies nearly 
horizontally; but the others stand more nearly vertically, parallel 
with the jaw and with the tooth in place, the youngest of the series 
being at the bottom. The whole row of tooth-sacs is contained within 
a single general connective-tissue investment, which is entered at the 
top by the descending process of oral epithelium, whence the enamel- 
