SOME OBSERVATIONS ON ACINETARIA. 657 
Robin’s belief that the vermiform individual is a young 
nematode, is of course quite untenable, and Strethill Wright’s 
view that the vermiform individual is a parasite protozoan is 
contradicted by :— 
(a) The fact that the nucleus of the vermiform is during 
the process of budding in continuity with the 
nucleus of the proboscidiform individual. 
(b) The identity of the ciliate embryos in the two forms. 
(8) The Developmental Theory.—This theory must 
be examined from two points of view :— 
(a) From that of the original belief of Claparéde and 
Lachmann, that the vermiform individual possessed 
a retracted proboscis and was identical with the 
proboscidiform individual. 
(b) From that of its later development in the hands of 
Fraipont and Sand according to which the vermi- 
form individual must be regarded as a develop- 
mental stage of the proboscidiform individual, this 
development consisting in a change in shape, the 
resorption of the characteristic rod-like stalk, and 
the formation of the proboscis. 
(A) Claparéde and Lachmann’s view is, I think, explained 
by the fact that in morbid vermiform individuals which have 
been kept some time under a coverslip, the cytoplasm towards 
the anterior end can contract away from the pellicule to fill 
the central cavity, and thus give the appearance of a dark 
central mass which might be taken for a retracted proboscis. 
Their fig. 2, Pl. 5, which is said to represent an “ Ophryo- 
dendron abietinum avec la trompe retractée” is quite clearly 
a young vermiform individual which has not yet formed its 
stalk. 
(s) There are no observations on the living Ophryodendron 
showing the development of the vermiform individual into 
the proboscidiform individual, and though I have frequently 
observed the same vermiform individual at intervals for 
periods of over forty-eight hours, I have never been able to 
see any indication of such a transformation. 
