SOME OBSERVATIONS ON ACINETARIA. 651 
and wander to a fresh position, but the bare stalks of the 
vermiform individual are often found attached to the 
hydroid. 
Fraipont and Sand’s view that the vermiform individual 
can develop into a proboscidiform individual will be examined 
in the concluding section, but it may be well to state here 
that I have never been able, either in continuous observations 
on the living animal or in fixed preparations to find the 
slightest evidence for this transformation. 
There is one interesting fact as regards the budding of the 
vermiform individual which I think points clearly to the 
conclusion that the vermiform individual is a_ distinct 
dimorphic individual. The size of the proboscidiform 
individual is very variable, whereas that of the budded 
vermiform individual is singularly constant even in those 
cases in which the parent proboscidiform individual is 
quite small (see text-fig. 5). 
This absence of correlation between the size of the parent 
proboscidiform and that of the attached vermiform bud is 
shown in the following table!: 
Proboscidiform individual. Vermiform bud. 
Greatest length of 
Greatest Greatest Greatest 
the body, exclud- 
ing the proboscis. breadth. length. breadth. 
Small Probosciditorm ; 34 20 138 | ii! 
| | 
| Medium Proboscidiform . 48 (Pe See TAS ea 2) 1 | 
| Large Proboscidiform . 92 | 46 184. 13 
These figures do not really express the difference in mass 
between the two individuals since the vermiform individual 
is cylindrical, and its width is more or less uniform through- 
out the greater part of the animal’s length, whereas in the 
proboscidiform individual, owing to its pyriform shape, the 
greatest width is far greater than the mean width. 
' Measurements in p. 
