340 Prof. R. Leuckart on the Developmental 
that has already been revealed to us by former observations for 
other groups of Entozoa. We see the brood of the Cucullanus, 
like that of the Tapeworm, quitting the bearer of their parent 
in the embryonic form; we see them migrate into an inter- 
mediate host, whilst here approach their later structure by trans- 
formations of various kinds, and finally attain their complete 
development after their transfer to their definitive host. 
There can be no doubt that in a considerable number of Ne- 
matode worms the life-history is exactly as in Cucullanus, and 
that this is the case not only in the family Strongylide, as above 
indicated, but also in other families, especially m that of the 
Ascaride. 
In the mesenteric covering of the stomach and intestines of 
athe mole we not unfrequently meet with pedunculated flat cap- 
sules, 15-2 millims. in diameter, which enclose a thread-worm, 
8-10 millims. in length, usually rolled into a flat spiral. This 
worm is an Ascaris (A. incisa, auctt.), but an Ascaris with un- 
developed sexual organs, and with a boring-tooth near the three 
tubercular buccal papille. This bormg-tooth was probably 
possessed by the worm in its embryonic state, and perhaps was 
employed by it in its wanderings in the interior of the mole. 
Its retention after the formation of the lips (which must take 
place very early, as I have seen them in young animals only 
1 millim. in length, with a capsule 0°4 millim. m diameter) 
seems to indicate that it will also be subsequently required. 
Perhaps, after the passage of the worm into its definitive host, 
it may use this tooth to break through the firm capsule which 
at this time envelopes it. The animal which constitutes this 
definitive host is at present unknown; but we may easily sup- 
pose it to be some of the numerous rapacious animals which 
prey upon the mole. In fact, the owls, buzzards, and other 
predaceous birds harbour in their intestines a round worm (A. 
depressa, auctt.), which, notwithstanding the more complicated 
structure of its buccal organs, may readily represent the deve- 
loped form of Ascaris incisa. The two forms agree especially in 
this respect—that they possess at the commencement of the 
chyle-intestine a ceecal diverticulum directed forward, which is 
usually wanting in the Ascarides of the Mammalia. I have, 
however, been unsuccessful in my attempts to develope A. incisa 
in the buzzard; but I had only a single bird at my disposal for 
this experiment, and moreover the buzzard may not be the 
animal. 
Perfectly similar encapsuled and asexual Nematode worms, 
with lips and boring-tooth, occur in numerous marine fishes, 
sometimes in the liver, but also sometimes (e. g. in the Torsk) 
in the muscles. As some of these are of considerable size (some 
