204 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Nussbanm and Ischikawa agree that ectoderm never becomes endoderm 
nor vice versa. But Nussbaum seems to have explained the restitution 
of the everted polyp by an active migration of ectoderm cells ; while 
Ischikawa showed that the Hydra righted itself after eversion by a 
genuine turning outside in. Ischikawa also demonstrated that endoderm 
cells were essential to the regeneration of a Hydra from a fragment, 
for the intermediary or interstitial cells cannot become endoderm. 
Weismann believes that the reason why an excised tentacle usually dies, 
and does not regenerate an organism, is not the absence of this or that 
kind of cell, but rather the small size of the fragment. 
Spongicola and Nausithoe .* — Signor Lo Bianco and Dr. P. Mayer 
have been able to demonstrate by following out the development of the 
larva the correctness of Metschnikoff’s suggestion that Nausithoe is a 
stage in the life-history of Spongicola Jistularis. The Spongicolidse are 
shown, therefore, to have nothing to do with the Hydroida, but to belong 
to the Acalephee. 
Porifera. 
Comparative Anatomy of Sponges.f — In the third of his studies 
on the comparative anatomy of Sponges, Mr. A. Dendy deals with the 
anatomy of Grantia labyrinthica Carter and the so-called family 
Teichonidae. Mr. Dendy is convinced that in the present transitional 
state of our knowledge of the Sponges anatomical investigation must 
precede systematic work ; the greater the number of types investigated 
the greater will be the value of the ultimate scheme of classification. 
One great reason for this is that polymorphism and homoplasy occur so 
generally and to such an extraordinary degree among the Porifera that 
a careful examination of the internal anatomy is above all things 
necessary. 
The structure of G. labyrinthica is described in detail and fully illus- 
trated. It was first called Teichonia by Mr. Carter, and the family of 
which it is the representative the Teiclionellidfe, which was altered by 
Polejaeff to Teichonidae ; in it that writer put his genus Eilhardia. As 
a matter of fact Eilhardia Schulzei Pol. and Teichonella prolifera Cart, 
are Leuconidae and G. labyrinthica is one of the Syconidae. 
In his fourth study;}; Mr. Dendy deals with the flagellated chambers 
and ova of the common British Sponge, Halichondria panicea. The canal 
system is of the lacunar type, the lacunae being so irregular as hardly to 
deserve the name of canals; the inhalant and exhalant lacunae are 
precisely similar and interdigitate with one another in the most compli- 
cated and irregular manner. The flagellated chambers, which lie wedged 
in between one lacuna of each kind, are in a general way subspherical in 
form ; their exhalant opening is very wide, and their diameter is about 
0*047 mm. 
The collared cells, when the chamber is seen in section, may be 
observed to stand some little distance apart from one another in the 
gelatinous ground-substance surrounding the chamber. Each cell has a 
short nucleated body, indistinguishable from the neck, and surmounted 
* Zool. Anzeig., xiii. (1890) pp. 687-8. 
t Quart. Jouru. Micr. Sci., xxxii. (1891) pp. 1-39 (4 pis.). 
X T. c., pp. 41-8 (1 pi.). 
