A NEW CUTANEOUS PARASITE, THE ENTOZOON FOULICULORUM. 
313 
longest specimen I have seen. The body of this animal, from the snout to the base 
of its posterior legs, measured and the greatest breadth of the thorax of 
an inch. Of the smallest there were two specimens, of which the same measure- 
ments were — 
Entire length. 
l 
100 
l 
100 
Length of body. 
l 
2 8 0 
1 
Greatest breadth. 
l 
48 0 
1 
312 555 
Of fifty specimens, the largest number measured in extreme length from to 
of an inch. In length of body the greatest number measured (in round numbers) 
, in length of head yoo ' o '? and in greatest breadth of an inch. 
2 7 5 
The short form varies in extreme length from twtt to 
of an inch. The shortest 
‘ S '- 11 100 109 
specimen that I have met with measured in length, namely, from the snout to the 
base of the posterior legs, g-^, and in greatest breadth 
? 5 5 o- 
that which measured in extreme length 
109 
The longest, namely, 
, measured in length of body 3 -^ 5 -, and in 
greatest breadth -g-g-Q of an inch. 
Turning my attention to the development and mode of growth of the Entozoon, I 
met with some curious results, — results that led me to the conclusion that the two 
varieties are developed in a manner peculiar to each ; that both proceed from ova, 
but that the larger kind pass through an intermediate developmental form in which 
the shorter do not participate. Probably this peculiarity may depend on some un- 
known modification of the elements of nutrition, and, very possibly, on the same 
cause with that which determines the greater length of the animalcule. In reflecting 
on this peculiarity I was reminded of the modification which the young of the com- 
mon earth-worm presents in a soil of variable tenacity, in the one case being extruded 
from the oviduct of the parent surrounded by a nidamental covering, and in the other 
in its perfect state. Plere is an important modification having reference to the 
security of the young ; the peculiarities in development of this Entozoon may have 
an analogous purpose. 
The ova of the Entozoon follicidorum are bodies of considerable size, and, as I 
failed in discovering any body of similar proportions within the abdomina of the many 
hundred animals which I have examined, I came to the conclusion that in their earlier 
state they were the nucleated cells which so commonly formed a cluster within the 
caudal extremity of the abdomen, and that these cells underwent development out of 
the body of the animal. I was strengthened in this view by occasionally finding small 
masses of these cells in the neighbourhood of the Entozoon. These masses were of 
an amber colour, and composed of nucleated cells, each of which measured about 
2 5 * 0 Q of an inch in the long and about one-fourth less in the short diameter. In the 
vicinity of the masses of small cells I frequently saw cells of somewhat larger size 
(Plate XVI. fig. 12 .) composed of secondary cells, and others, of a more or less oval 
shape, containing within their investing membrane secondary nucleated cells of 
various size and in considerable number (Plate XVII. fig. 13.). The measurement of 
2 s 2 
