SUMMARY OF CURRENT RESEARCHES RELATING TO 
308 
II. Plurilocular sporanges, which form 
a. Gametes. 
a. Normal male and female gametes. 
/3. Parthenogenetic gametes. 
y. Aplanospores. 
b. Neutral swarmers. 
a. Normal swarmers. 
/3. Aplanospores. 
Chambers and Pores in the Cell-wall of Diatoms.* — Herr 0. 
Muller records a number of minute observations on the structure of 
the siliceous valves of Isthmia nervosa , Eupodiscus Argus , and Epi- 
themia Hyndmanni , and concludes with the following observations. 
“ The perforation of the cell-wall by pores and canals, with or 
without relation to areolar chambers, is a frequent phenomenon, and 
offers a wide field for the investigation of the finer structure of the 
cell-wall. But the similarity of external conformation does not 
necessarily imply similarity of function. It is certain that the 
pore-canals of Eupodiscus have a different function from those of 
Isthmia. The former genus has no special contrivances for osmosis ; 
the pore-canals carry the protoplasm to the chambers which open out- 
wards, where interchange with the external medium takes place by free 
diffusion. In Isthmia , on the other hand, there is abundant osmotic 
apparatus, and the pore-canals must have a different still unknown 
function, although the protoplasm contained in them, and possibly 
escaping through them, must obviously take up salts and oxygen from 
contact with the external medium. If, in the cases of Eupodiscus , 
Triceratium , Pleurosigma, &c., the pore-canals have a second unknown 
function in addition to diffusion, which, in Isthmia, Epitliemia, &c., is 
assigned to the special pore-system, we must regard the latter as ex- 
hibiting a distribution of labour which is not displayed in the former. 
While Pleurosigma has a countless number of extremely minute chambers 
and pores, which give the cell-wall the appearance of a sieve, the cell- 
wall of Pinnularia is provided with large chambers opening outwards, 
and is nowhere perforated by pores except at the raphe. Both genera, 
however, have a raphe, and the presence or absence of this structure 
cannot therefore influence the purpose in the economy of the cell which 
is provided for by these contrivances.” 
Movements of Diatoms.f — Mr. F. R. Rowley gives a careful abstract 
of Lauterborn’s important work J on the Structure, Division, and Move- 
ment of Diatoms. The structure of the frustule of Pinnularia major 
and Surirella calcar ata is described in detail. In the former species 
Lauterborn believes in the existence of an enveloping layer of hyaline 
jelly, so remarkably transparent, and possessing a refractive index cor- 
responding so closely with that of the surrounding water, as to be 
completely invisible in clear water, even with the best lenses. The 
motion is probably due to very fine gelatinous threads, proceeding from 
the central node, and running obliquely backwards, forming an acute 
* Ber. Deutsch. Bot. Ges., xvi. (,1898) pp. 386-402 (2 pis.). 
t Natural Science, xiii. (1898) pp. 406-16 (1 pi.). 
X Cf. this Journal, 1897, p. 234. 
