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pseudo-filaria. If these vermicular filaments had not been 
seen developing under one’s eyes at the expense of a cytod, 
it would be difficult to believe that they were not young 
Nematoids. We know, in fact, that it is always extremely 
difficult to distiriguish cellular elements in these little worms, 
and often it is not possible to detect, except with great 
trouble and in a very obscure manner, any trace of a di- 
gestive tube. It is the “ pseudo-filaria” of the Gregarine 
of the earthworm in all probability which have been taken 
for young Nematoids, and we have here clearly enough the 
explanation of the very erroneous opinion which has pre- 
vailed, according to which the Gregarine are only a phase 
in the development of the Nematoid worms. This opinion 
has been defended by naturalists of the first rank, such as 
Henle,! Bruch,? Leuckart,? and Leydig.* 
In 1845 Henle expressed himself thus as to these rela- 
tions between the Gregarine and the Anguilluloid parasites 
of the earth-worm:'—“ It has become my conviction that 
the Gregarine of the earthworm stand in the same relation 
to the Anguillula-like Entozoa of the same animal, as, ac- 
cording to Miescher, do the rigid chrysalids in the intestines 
of many fish to the Filaria piscium. I have detected a series 
of transition forms between Anguillula and the Gregarina, of 
which some haye been already described by Dujardin ® as 
Proteus tenax, and by Sarissay’ as Sablier proteiforme. The 
Anguillula becomes stiff, and its intestine breaks up within 
the outer skin into a granular mass, whilst the form of the 
body is changed from an elongated into an oval or spheroidal 
form.” 
Whilst Bruch and Henle admitted the possibility of the 
transformation of worms similar to young Filarie into Gre- 
garine, Leydig, according to observations made on the pa- 
rasites of a Terebella, was more inclined to believe in a 
metamorphosis in the other direction—that is, from Gre- 
garinz into Nematoids. 
It is not to be doubted that it is the analogy between the 
forms and the movements of these protoplasmic filaments, 
which I have just described under the name of “ pseudo- 
filaria,’ with young Nematoids, which has caused these 
1 Henle, ‘ Miller’s Archiv,’ 1845. 
2 Bruch, ‘ Zeitschrift fur Wiss. Zool.,’ t. ii. 
3 Leuckart, ‘ Archiv fiir Phys. Heilkunde,’ xi, 1852, p. 429. 
4 Leydig, ‘ Miiller’s Archiv,’ 1851. 
5 In his ‘ Jahresbericht fiir Histologie,’ 1845. 
6 * Annales des Sciences Naturelles,’ 2nd series, t. iv. 
? Tbidem, 2nd series, t. vi. 
