SOME OBSERVATIONS ON ACINETARIA. 631 
great in fact that two at least among its observers, Strethill 
Wright and Robin, have described the vermiform animal as 
a parasite), in the one case as a Gregarine, in the other as a 
Nematode worm, but before proceeding to give any further 
account of the life-history of the animal, it will be necessary 
to examine shortly the very discrepant views as to the rela- 
tions between the two individuals put forward by earlier 
workers on this animal. 
2. HiIstToricat. 
Ophryodendron abietinum was first discovered by 
Claparéde and Lachmann in 1855 on Campanularia from 
the North Sea. Their account of this animal is in many 
respects by far the best which has yet appeared since they 
saw and figured the free ciliated embryo. 
On the other hand, although they recognised the difference 
in external form between the vermiform and the proboscidi- 
form individuals, they finally concluded that in the vermiform 
individuals the proboscis was retracted, and that therefore 
there was no fundamental difference between the two forms 
(p. 143, “‘l’extremité anteérieure de ces espéces de vers pré- 
sentait une espece d’enfoncement spécial, que nous crimes 
@abord devoir considérer comme une bouche ou comme une 
ventouse de succion, mais que nous reconniimes bient0ot n’étre 
qwune fossette indiquant Llouverture d’une cavité dans 
laquelle était logé un long organe rétractile que nous aurons 
a décrire plus loin”). 
They recognised in the interior of some animals both of 
the vermiform and proboscidiform type small corpuscles 
“tout a fait semblables aux organes urticants des Campanu- 
laires” (p. 144), but as all their efforts to surprise the animal 
at the moment of feeding were vain (p. 145), they concluded 
that “les corpuscles particuhers quwils renferment sont peut 
étre comparable aux trichocystes d’autres infusoires.” ‘hey 
thought it probable that the proboscidiform individuals could 
