6 Prof. F. Schmitz on the 
directly connected by numerous cords, which principally 
(sometimes apparently exclusively) perforate the closing 
membrane at the periphery of the pit, and here often coalesce 
laterally into hollow cylindrical bands*. 
On the other hand, however, these plates are directly and 
firmly coherent with the parietal protoplasm of the cell, and 
apparently form only the completion of the parietal proto- 
plasmic sac T along the surfaces of the pits; in reality, how- 
ever, they are probably, at least towards the lumen of the 
cell, coated with a very thin layer of protoplasm. In dead 
material, the cell-walls of which usually swell up more or 
less in a gelatinous form, the pairs of lami remain united, 
and in accordance with this we see the contracted plasma- 
body of all the individual cells more or less drawn out into 
cord-like processes towards the neighbouring cells, connected 
together by means of these pairs of lamine. 
Thus by means of the cords which traverse the closing 
membranes of the pits and unite the two lamine of the diffe- 
rent pairs, a direct connexion of the neighbouring cells with 
one another is established, and thereby a direct union of all 
the cells of the thallus is attained}, enabling these thallus- 
cells, notwithstanding their extraordinarily great number, by 
unitary cooperation to form a single whole, a single indivi- 
dual plant §. 
mens of Griffithsia Schousbwt, J. Ag., and Pterothamnion plumula, Nag., 
which had been hardened with picric acid. 
* How far analogous closing-plates also belong to the pits of other 
Algw (Fucacez, Dictyotacee, Volvocacez, &c.) can only be decided by 
further investigation. The fact that, on the contraction of the plasma, 
plasma-cords remain pretty regularly attached to these pits, leads one to 
expect similar conditions in the structure of these pits. But the small 
size of most of these structures greatly increases the difficulty of deciding 
the question with certainty. 
+ Whether these lamin are produced by local differentiation (chemi- 
cal transformation) of the parietal protoplasm, may for the present remain 
an open question. I regard this, however, as not improbable. 
{ The direct connexion of all the cells of the thallus by means of these 
pits has already been indicated by Bornet (‘Etudes Phycologiques,’ 
p- 100), who, however, regards these pits as perfectly open canals. He 
even endeavoured, through this direct connexion of all the thallus-cells, to 
explain how, from the fecundated female cell, the fertilizing influence 
propagates itself to that cell which grows into the spore-fruit. 
§ In my opinion these connecting cords between the two closing plates 
of the pit serve essentially for the transference of dynamic influences from 
cell to cell; the corresponding pores of the cell-membrane, however, at 
the same time render possible a readier exchange of dissolved substances 
between the two neighbouring cells. A migration of protoplasm itself 
from one cell to another by means of these open communications I regard 
as inadmissible. 
Various facts indeed seem to me to favour our regarding the two 
