ZOOLOGY AND BOTANY* MICROSCOPY* ETC. 
365 
particular genera or families, to which. Thilenius objects that this pre- 
supposes a complete knowledge of comparative anatomy. Thus, a few 
years ago the radiale externum would have been ranked in this division, 
but no one would now admit this. Emery’s second division includes 
parts which are typical for Mammals, but have been secondarily added, 
for instance to the original chiridium, as is shown by their absence in 
other Vertebrates. He gives the metacarpo-phalangeal sesamoids as an 
example ; but Thilenius notes that he has suggested the presence of 
sesamoids in the anomodont Keirognatlius cordylus, and that Nassonov 
has described hyaline cartilage preformations of metacarpo-phalangeal 
sesamoids in the ostrich. Emery’s third category includes accessory 
parts falsely so-called ; and to this Thilenius has no objection, except 
that he questions whether it does not include all the cases. 
An appeal has been made in this connection to the supposed ontogenic 
recapitulation of phylogeny, but the author places little confidence in 
this. The phyletic time-succession is not observed ; the Vertebrate 
central nervous system appears in the gastrula stage, the heart is present 
and functioning before there are capillaries, the wisdom-tooth is surely 
not phyletically younger than the others. In fact, the ontogenic suc- 
cession is influenced by the physiological importance of the parts, unim- 
portant parts being slowed, important parts being hastened. Therefore 
one «cannot determine phyletic age by time of ontogenic appearance. At 
the same time, ontogeny is of much importance in showing the process 
by which the adult state is reached, by revealing parts which are absent 
or rudimentary in the full-grown form, and by exhibiting structural 
conditions of ancient date, as in the pentadactyl Anlage of the bird 
hand. 
“ Accessory,” like other parts of the skeleton, may be represented in 
the embryo by preformations in connective tissue, e.g. the Wormian 
bones of the skull, or by preformations in hyaline cartilage, e.g. the 
metacarpo-phalangeal sesamoids. Neither here nor in histological dis- 
tinctions can the conception of strictly novel accessory parts find at 
present any secure basis. 
Venoms of Toad and Salamander.* — Dr. E. T. Hewlett gives an 
account of recent researches and of his own investigations into the 
cutaneous secretions of the toad and salamander. Both animals secrete, 
from special skin-glands, an intensely bitter venom, differing entirely 
from snake-poison in that it is alkaloidal, not proteid. The venom of 
both, if subcutaneously injected, is fatal to birds, dogs, and guinea-pigs ; 
administered by the mouth, that of the toad produces only vomiting, that 
of the salamander is toxic only in large quantities. Phrynin, or bufidine, 
the active principle of toad-venom, has an action on respiration and cir- 
culation not unlike that of digitalis; salamandrine is predominantly 
convulsive in its action, and has no direct effect upon the heart. The 
venom is fatal to the animal which secretes it only when administered 
in comparatively large doses ; but an ordinary dose of the venom of the 
toad or the newt kills the salamander, and an ordinary dose of salaman- 
drine is fatal to the newt and the toad, though all the secretions have a 
general similarity in action. 
* Science Progress, i. (1897) pp. 397-405. 
