246 REPORT OF THE COMMISSIONER OF FISH AND FISHERIES. 
pressure on the cover-glass they can be separated almost completely. 
They remain, however, connected at the posterior end; ridge present. 
On longitudinal (“end”) view the valves are seen to unite with 
each other, either by direct fusion and without appreciable line of 
demarcation, or to be soldered by the thick interiorly projecting welt- 
like ridge (in optical section, circular). 
Weltner believes that the tail structure (in this species) always con- 
sists of a superior and an inferior half, each half being a process of the 
corresponding valve. For, in the very few cases in which the valves 
diverged posteriorly (remaining connected anteriorly), he saw this quite 
plainly; with some shells the tail-halves were shorter; with others 
longer; also inequality of length is very frequent in the same spore, 
and one valve-process may be very long and the other very short. 
Other spores have only one valve sharply drawn out, the other showing 
no trace of a tail. Tail thinner than that of MW. psorospermicus (Lieber- 
kiihn’s figures in Biitschli). 
The spores in which the tail is double may lie in 3 positions:' (1) 
Most frequently the tails are plainly visible only on a transverse (or at 
least an oblique) view. The tail-halves (which on vertical view cover 
each other) then diverge. (2) With other spores things are different; 
here the tail-halves appear side by side, on vertical view. (3) The third 
position is that in which the tails cross (in the manner of a crossbill’s 
beak) both on vertical and transverse views. 
Capsules: 2, fusiform, length 5-1 to 5:9 jw; their posterior end 
bluntly rounded off and often obliquely truneated.? The separated 
capsules are rounded pyriform. Capsules mostly parallel-appressed, 
mutually flattened. in spores whose capsules lie separated from each 
other the granulated sporoplasm is seen between them. Longitudinal 
(“end”) views show the capsules to be imbedded in the sporoplasm. 
Weltner only once certainly observed the sporoplasmic covering to 
extend as far forward as the apex of the capsules. The latteris always 
clear and glistening when containing the filament; dull when empty. 
The capsule of the present form differs from that of M. psorospermicus 
(Lieberkiihn’s figures in Biitschli) in shape; also here the capsular index 
is smaller. In M. schizurus the shape and position of the capsule is 
also different. 
Filament: Not visible (under a power of 1,090 diameters) through the 
capsular wall; only a dark shadow being seen. Exit produced by 
glacial acetic acid; also (spores in alcohol), by pressure on the cover 
glass; the last method produced the extrusion of many filaments; 
extruded filaments often quite straight; length, 47:9 yu. 
1 It seems to me that all this is produced merely by a slight lateral shifting of the 
valves and by the flexibility of the tail. At any rate all these aspects are so produced 
in M. cf. linearis (see p. 254). 
2A similar apparent marked truncation is an optical illusion in A. macrurus. 
es 
