The Mode of Growth of Tubicinella Trachealis. D 
soon be thrown off as the outer layers of the epidermis became 
deteriorated and worn away. But the Twbicinella has not only to 
attach itself, but also to penetrate into the epidermis to a depth of 
one inch and a half, and that although its base is formed by a 
delicate membrane. 
Seeing this, it occurred to me that the animal possibly secreted 
some fluid which possesses the power of dissolving the epidermis. 
Such secretions, which contain peptonising ferments, e.g., pepsine 
or pepsine-like bodies, and which are capable of rendering soluble 
the albuminous matter of animal bodies are well known in the 
vegetable kingdom as well as among animals. The sundew, and 
many other so-called insectivorous plants digest the albuminous 
matter of insects and other animals in this way, and the same is 
done by many arachnids and insects with their prey. 
In order to test this theory, I removed some living Twbicinellas 
from the skin of the whale, placed their lower side in direct contact 
with pieces of boiled albumen (white of an egg), and poured sea-water 
into the vessels until the base of the shell was immersed.* After 
some time, varying from half an hour to twenty-four hours, I analysed 
the liquids. The soluble albuminoids were removed by saturating 
each liquid with sulphate of zine, allowing it to stand for twenty-four 
hours, and filtering it. The filtrates were treated with hydrate of 
potash and sulphate of copper, and in each case I obtained positive 
reactions for the presence of peptones. This proved that a pepto- 
nising ferment diffuses through the basal membrane of the animal, 
and this fact explains the peculiar structure of the animal as well 
as that of the skin of the whale at the infested parts of its head. 
The young Twbicinella simply dissolves the epidermis with which it 
is in contact, absorbing the peptonised liquid. As it continually 
grows at its lower end it gradually descends in this way into the 
epidermis, the digesting of the epidermal layers taking place at the 
same rate as the downward growth. 
When the parasite has reached its maturity, its shell is just as 
long as the epidermis is thick, viz., about one inch and a half, a 
thin layer of epidermis, about one-tenth of an inch in thickness 
remaining underneath each parasite between its base and the corium 
of the skin. 
The presence of the peptonising ferment having been proved, it is 
not necessary any more to assume that the epidermis stops growing 
underneath each parasite. On the contrary, its uniform growth 
would produce exactly the structure of the epidermis as we find it. 
If the parasite did not secrete such a ferment, the layer of epidermis 
* The Tubicinellas remained alive for two or even three days. 
