8 Gcel. 
CCELENTERATA. 
Schneider (80) gives an account, illustrated by numerous figures, of a 
detailed investigation of the histological structure of Hydra fusca. He 
describes the nerve-cells and nerve-fibrils found in the ectoderm, and 
considers that the epitlielio-muscular cells should no longer be termed 
“ neuro-muscular ” cells, since the nerve cells and fibrils probably perform 
the same functions as the nervous tissues of other Metazoa. Although an 
organic connection between the nerve-fibrils aud nematocysts has not yet 
been demonstrated, it seems probable on physiological grounds that such 
a connection does exist. Important details concerning the minute struc- 
ture of the three different kinds of nematocysts and of the endoderm 
are given. 
In Tubularia larynx and Eudendrium ramosum a system of ganglion 
cells and nerve-fibrils was found, answering in structure and position to 
those of Hydra. 
Boveri (13) finds two polar bodies are protruded from the ovum of 
Tiara (sp. P). 
Chatin (15) denies the existence of free nuclei in the ovary of Hydra. 
Each nucleus is surrounded by a delicate layer of protoplasm, 
Driescii (22) continues the account of his investigations on the forma- 
tion of the hydroid colonies, He finds (25) that in Sertularella polyzonias, 
the stolons produced in unfavourable positions are at first positively, and 
— after the production of daughter-stolons — negatively, heliotropic. 
McIntosh (67, 1) describes some Medusae that are apparently abnormal 
forms of Thamantias melanops. The reproductive bands form a conspicu- 
ous cross over the disc. There is no mouth and no manubrium. 
Fowler (31) found two specimens of the hydroid polyp of Limnocodium 
sowerbyi throwing off Medusae. The bud of a new hydroid polyp differs 
from the parent only in the uniform cubic shape of the ectoderm cells, in 
the absence of a mouth, of nematocysts, and of the little mass of cells 
probably answering to the “ Glockenkern ” that is present in the parent, 
and in the non-differentiation of the endoderm into two regions. The 
medusa, in the only specimen examined, was found at the apex of the 
polyp. At the apex, the ectoderm grows inwards to form a solid plug of 
cells, which probably represents the praeumbral lid, and a somewhat 
globular mass of more vacuolated cells, which forms the sub-umbrella 
cavity. These two masses of cells represent probably the “ Glockenkern.” 
Hickson (42) describes the lenticular mass of cells that supports the 
large telolecithal egg of Allopora , and proposes that it should be called 
the “ trophodisc.” The trophodisc is formed by the folding of one wall 
of a ccenosarcal canal that contains an ovum. It rapidly becomes more 
and more complicated as the ovum enlarges. Soon after the ovum is 
fertilized, the trophodisc atrophies. The ovum does not undergo a pro- 
cess of segmentation. The germinal vesicle, after fertilisation has taken 
place, fragments, and the ectoderm is formed by a process similar to free- 
cell formation. The embryo escapes from the colony as a solid planula. 
Hickson (44), in a preliminary note . on the meaning of the ampullae of 
Millepora murrayi, states that they are occupied by modified dactylozooids 
