8 Goal 
CCELENTERATA. 
originate in the endodermal layer. Again, in Podocoryne, the sexual 
products (ova) are developed in the ectoderm, according to Grobben 
(10) ; in Luccrnaria, in the endoderm according to Korotneff (14) ; 
this author however tries to reconcile the contradictory observations by 
the explanation, that they are, in fact, in all Co&lenterata and Sponges, 
developed in the mesoderm, in some instances outside of, in others inside 
of the hyaline membrane, and therefore apparently in the ectodermal or 
endodermal layers, respectively. Korotneff further criticises the state- 
ments of Kleinenberg concerning the histology of Hydra, and gives an 
explanation of its muscular ectoderm more in accordance with the histo- 
logical structure of other Hydrozoa. Among his own contributions to 
the histology of Lucernaria, the existence of a micropyle in the ovum 
and the fibrillary connection of the nematocysts of the tentacular heads 
with more deeply situated simple or multipolar (nervous ?) cells, may be 
entitled to peculiar attention. 
To the valuable experimental investigations of Romanes (20), it is 
impossible to do justice in the brief space allowed here to statements of 
facts; it must, however, be mentioned that his physiological experi- 
ments demonstrate the reality of the nervous system, the existence 
of which was positively asserted by L. Agassiz, and that the marginal 
organs (e.y. in Sarsia) are in fact organs of vision, or at least of per- 
ception of light. In the naked-eyed Medusai, the centres of spontaneity 
are experimentally shown to bo localized in the margin of the nectocalyx, 
and especially, but not exclusively, in the lithocysts ; in the hooded-eyed 
Discophora their localization in the marginal portion of the disc is less 
exclusive, but, on the other hand, as far as the margin is concerned, more 
sharply constricted to the eight lithocysts. 
The admirable paper by Allman on Myriothela (2) has largely advanced 
the knowledge of this remarkable type, and indirectly thrown light upon 
the intimate structure and physiology of Hydroids generally. The large 
single worm-like hydranth is provided near its basal extremity with a 
chitinous perisarc and with short organs of attachment ; its distal por- 
tion with a number of short capitate tentacula ; below the tentacular 
region is the zone of the blastostyles (proliferous polypites), without 
a mouth, but with some capitate tentacula ; a third set of zooids are the 
“ claspers,^’ thread-like bodies with a slightly dilated distal extremity, 
placed commonly in pairs near the base of the blastostyles. On these 
the gonophores are developed, male and female together, often on the 
same blastostyle. While still enclosed within the gonophore, the “ ova ” 
coalesce into a sort of “ plasmodium,’’ covered by a thin structureless 
membrane ; when set free through the opening and retraction of the 
maternal gonophore, this plasmodial egg is seized by one or more claspers, 
and retained there until the bursting of the membrane and the liberation 
of the embryo Actinula. In what manner the fecundation takes place has 
not l)een observed, but probably the spermatozoa wanders into the gastric 
cavity of the hydranth, through the “ spadix ” of the male gonophore, 
and communicate with the plasmodial egg through the cavity of the 
“ claspers.” The long, capitate, thread-like preliminary tentacles of the 
“ Actinula,” which afterwards disappear during the evolution of the 
