292 RECENT RESEARCHES IN THE DIATOMACER., 
purpose many cells unite in a common gelatinous suyelopna on the 
extremities of the fallen, or smaller expansions arise on the sides and 
middle seh the tubes That mother- ieee then develope ven —— 
e structures described by Kiitzing, Bac., p. 112., t. 23, f. i1., 
a be, as the fruit of Petlope tenuis, (Kitz, ), appear to me, adds Pfitz Pe 
not to belong to the Bacilariacee at all. It appears then that, so far 
as the internal structure of the cell is concerned, dighoiard bears a 
strong resemblance to Wavicula. 
n case the character noted by Pfitzer—namely, the development of 
a central nodule on one median line, by which I understand its occur- 
“rence on one valve and not on the other—be sustained by fact, the 
position of Amphipleura will be nines affected. In special reference 
to this subject I ve examined very many specimens of Amphipleura 
pellucida, and could observe no trace in any of a central nodule. 
Oe, devon ces 
keel, which, instead of bei g central, is mine t excentric ; and als 
by the isappearance of the prominent longitudinal stria, which 
along with the same occur the hipr The valve of P. 
xcentri 
valye-surface to the seer Na on the valve the keel deviates 
towards the right, on the under valve iwords the left, so that Plagio- 
tro opis, like fees toe is diagonally constructed. The valves exhibit 
nd whe The 
c 
which it has extended, the opposite margin going a shorter distance 
towards the other heel. The structure of the soft cer corresponds 
with the diagonal construction of the cell-cover 
Amphitropidee. 
n this group we have only a single form, Anieriteasis agar 
(Rabe ), quere Amphicampa paludosa, Rab. F). Bur. Alg., p. 257. The 
Amphitropidea, says Pfitzer, are related to the Plagiotropidee some- 
what asthe Cymbellea, still symmetrical in outline, are to the Naviculee. 
ee 
