Fossil and Recent Infusoria. 373 
one, or contemporaneously many exterior warts (gems) without 
- any change in its interior.. An animal which is capable of divis- 
ion first doubles the inner organs, and subsequently decreases ex- 
teriorly in size. Self division proceeds from the interior towards 
the exterior, from the center to the periphery; gemmation, 
which also oceurs in animals; proceeds from the exterior towards 
the interior, and. forms first a wart, which then gradually becomes 
guasee: ! 
ce. discussion now arose between Prof, Rymer Jones and me. 
Prof. Jones observed, that although he had himself taken great 
pains, yet he had. never been able to see the structure described 
by me of the interior organization, viz. of the alimentary canal 
of the polygastric Infusoria, although he had found the external 
forms to be exactly the same. He had not been able to discover 
any trace of an alimentary canal, andin Paramecium Aurelia and 
other species he had observed a circular motion of the inner 
cells which could not agree with the formation I had described. 
I answered him, that such discussions then only could lead to-a 
result when they do not merge into general but enter into special 
cases. “Ihe mass of relations of organization, which after many 
years of observation have been gradually established, could not be 
_ brought into question by-a single doubtful fact. The perfect orgaie 
ization of the wheel animalcules had been established beyond 
question. With regard to Paramecium Aurelia, this is one of 
those forms unfavorable to suck observations ; and it had been ex- 
pressly observed by me that Imyself had not boon able to recognize 
the alimentary canal in all species of the various genera ; but on the 
other hand it was quite evident in a very cosisidesabla number of 
species and genera. I stated that in my present work this subject 
had been treated of in detail, and that those forms in which the 
relations are perfectly evident have been pu rposely enumerated, 
Some of these forms I then exhibited in the drawings, and con- 
cluded with the remark that the circular motion observed by Prof. 
Jones had already been treated of by others, (for instance, Dr. 
Foeke,) and had naturally been frequently observed by myself. 
The great contractibility of the body of the animalcule was, to 
less practiced observers, frequently a cause of enigmatical phenom- 
ena, of which continued patient observation of the object would 
gradually bring the explanation. ‘Thus, at times, the intestinal 
: - Canal of the animalcule extends at the expense of the ventral 
