552 SUPPLEMENT 
ferent individuals, and sometimes of such parts on the same 
individual; at other times of female parts alone, and in fine, 
we sometimes find scarcely any indications whatsoever, of this 
apparatus. ; 
The existence of a nervous system in these animals is very 
doubtful, at all events in those which may be properly termed 
entozoa. No one has been able to recognize any thing of the 
sort in the tanize, or neighbouring genera. 
The organization of the product of generation in both, in 
the exterior and interior worms, has not been sufficiently 
studied. Such eggs as have been discovered are oval, and 
very regularly formed. They all appear to be in reality eggs, 
with a distinct envelope containing grains. But this was the 
most that could be distinguished, even with the microscope. 
The physiology of worms presents nothing which can really 
be considered as peculiar to themselves. 
Their general sensibility appears to be considerable. In 
fact, at the slightest contact of a solid body, or even of a 
liquid of a heat or nature different from that in which they 
are plunged, they torment themselves, and twist about in 
all directions. The tenize do this almost as much as the 
others, but only in a less extended portion of their body at 
once. A special sensibility they do not seem at all to pos- 
sess, nor any perception of bodies, whether by savour or odour, 
and still less by the luminous rays which they send forth. 
The contractility of worms is evidently very great, and 
that almost in all their tissues, so that they have considerable 
power of changing form and dimensions, as may be particu- 
larly observed in some of them, which are almost in a conti- 
nual state of agitation. ‘Their locomotion is, therefore, some- 
times tolerably active. 
They seem, in general, to possess but little tenacity of life. 
Some, indeed, such as tenia, have been observed to live 
many hours after having been extracted from the intes- 
