History of the Nematode Worms. 337 
verminous pneumonia (proceeding from Strongylus filaria) must 
therefore be without foundation*. 
The immigration of the young worms into their definitive host 
appears to take place only when they have grown to at least twice 
their original length; at least I conclude so from the analogy 
of Ollulanus. The smallest specimens observed by me measured 
3-5 millims. They were found several times in the trachea of 
healthy sheep, and were not yet sexually developed. When their 
length has increased to 9-12 millims. the worm is found in the 
interior of the lung. Sometimes they appear to die even in this 
stage ; at least I once found in the lung of a sheep a number of | 
small, tubercle-like knots, each surrounded by a space of hepa- 
tized tissue, and enclosing a dead and coiled up Strongylus of 
the above-mentioned size. 
With regard to the development of the last-mentioned 
Strongylide worms, I have been compelled to confine myself to 
mere suppositions; in other cases I have again been fortunate 
in my experiments. 
Thus, especially, I have succeeded in tracing experimentally 
the entire developmental history of the so-called Hooded Worm 
(Cucullanus elegans). The worm, which in the developed state 
measures about 20 millims. in length, lives in the intestine and 
pyloric appendages of the perch, and is so abundant as to be 
found in nearly every specimen of the fish. Among its most 
important distinctive characters is, as is well known, its posses- 
sion of a horny buccal funnel equally remarkable for its size and 
the elegance of its markings—an organ which is also certainly 
met with elsewhere in the family Strongylide, but in a different 
form. 
The female Cucullani produce living young, which escape 
from the egg-capsules whilst still within the body of the parent, 
and, in large specimens, may be found in many thousands in 
the sexual passages. Unlike the embryos of the other Strongy- 
lide, they are furnished with a long subulate caudal extremity, 
which measures neatly one-third of the total length of the body 
(0-4 millim.), and possesses an extraordinary mobility. In a state 
of repose the animals are usually bowed or rolled up spirally ; 
several of them may also not unfrequently be seen adhering to- 
gether by their tails and making powerful jerking movements. 
The cuticle is uncommonly firm, and distinctly ringed, and cha- 
racterized by a hump-like thickening on each side at the level of 
the anus. A similar thickening is observed on the dorsal mar- 
* It is also opposed to the fact that the young embryos (as also in S. 
commutatus and S. rufescens) never undergo any further metamorphosis 
in their birthplace. 
Ann. & Mag. N. Hist. Ser.3. Vol. xvii. 22 
