798 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
convince oneself that a nucleus is attached to each otolith ; in Hormiphora 
and Callianira the otoliths are much more firmly attached to one another, 
hut between them there are thin protoplasmic walls, to which the nuclei 
are often attached. The otoliths, therefore, are not, as has been hitherto 
supposed, cell-products but epithelial cells themselves which have 
become set free from the epithelium. There is a unilaminate ciliated 
epithelium in the polar plates, and there is no difference between the 
plates; the author, therefore, is unable to confirm the statement of 
v. Lendenfeld that there are special spindle-shaped sensory cells in the 
polar plates of Neis. 
The structure of the tentacles is dealt with in some detail, and it is 
concluded that the facts point pretty clearly to the mesodermal origin 
of the axis of the tentacle ; the so-called seizing cells appear to be 
composed of at least two cells, the glandular portion of which is funda- 
mentally the same as the glandular cells of the epithelium ; neither in 
Callianira nor in Hormiphora does the tentacular apparatus contain any 
cells which can be regarded as nervous. 
The author’s examination of the tissues leads him to the conclusion 
that the Ctenophora have no nervous system, although he believes them 
to be in a condition which must have preceded the formation of the 
nervous system in bilateral animals. Kleinenberg and the Hertwigs, in 
their speculations on the origin of the nervous system, have postulated 
a primary connection between it and the musculature ; but one system 
is ectodermal, the other mesodermal in origin ; the connection between 
the two is, therefore, secondary. 
If, without any regard to phylogenetic speculations, we examine the 
facts of development we find that an ectodermal nervous system and a 
mesodermal musculature exist for a time independently of one another. 
Though a musculature without a nervous system is possible, a nervous 
system without a musculature is unthinkable, for it would have no 
function. If, therefore, it existed it must have had some other function. 
This condition appears to be represented in the Ctenophora ; they 
possess a mesodermal musculature which functions without the inter- 
mediation of a nervous system. The sensory bodies and the median 
bands are regarded as the predecessors of the nervous system, and in the 
Ctenophora there are various stages of development which lie on the 
direct road to a conversion into a nervous system. 
The Lobatse and the Cestidac exhibit the primitive condition, the 
ctenophoral plates being connected by ciliated bands ; the whole 
meridian band consists of a continuous row of ciliated cells, which appear 
to be specially modified only in the ctenophoral plates. In Callianira 
and Hormiphora there are no ciliated bands between the basal cushions ; 
these are connected by fibres which may, physiologically, have a nerve- 
like function ; but these fibres possess no nuclei, they are merely con- 
tinuations of cells of the cushion. The next stage is seen in Beroe ; 
here the epithelial cells of the basal cushion are separated from the rest 
of the epithelium, and are connected with fibres which connect the 
cushions with one another. Physiologically they clearly have a nerve- 
like function, and as they have also the histological characters of nerve- 
fibres, there is no reason why they should not be called so. But, in 
Beroe , the musculature is also considerably altered ; while in Hormi- 
