€6 General Notes. 
had been peeled oS of the surface of the floating timbers. These 
masses were traversed superficially by a mat of fibres which were 
found to be derived from the outer tunic or mantle of the Ascidians, 
by means of which the latter were adherent to their support. 
At first, in separating the "" " -^ • • 
of support, it was supposed t 
gether due to their having been caught during the very early veliger 
stage in this mat of fibres formed about the bases of the Ascidians. 
As they grew larger it was further supposed that they were held fast 
in their unusual position by the fibres and cement substance secreted 
hy the mantles of their Ascidian neighbors, and thus were suffered 
to attain a considerable size (from two to fifteen millimetres) before 
they finally became free and sank into a more favorable position on 
the bottom. However, further investigation showed that in this I 
was in error, for after a careful search, a few individuals were found 
from which a single byssal thread was found to proceed, invariably 
from the point where the tip of the foot is thrust through the me- 
dian opening in the mantle. To make it still more certain that 
there should be no mistake, the byssal thread was pulled out of its 
insertion in several specimens, when it was found to present the 
irregular swollen proximal end usually found to characterize the in- 
traglandular portion of the byssus in molluscs which possess this 
organ. The subject at this point became sufficiently interesting to 
warrant farther study, and, inasmuch as but a few individuals were 
found which had the byssal thread in place, that structure being 
usually torn loose in removing the specimens from their support 
amongst the Ascidians, it became necessary to resort to the meth- 
ods of sectioning to determine if there was a byssal gland present in 
the foot. 
To this end a number of specimens were treated first with a dilute 
chromic acid solution (one-half per cent.). After this had fixed the 
tissues, the solution was renewed and acidulated with nitric acid 
(one-half per cent.), and allowed to act until all of the calcareous 
matter had been removed from the shell. This left the specimens 
in good histological condition for cutting, after which the specimens 
were washed, dehydrated, and saturated with celloidin, in which 
they were embedded and sectioned on a Schanze microtome. 
The sections were cut parallel to the median longitudinal plane, 
or so as to coincide with the union of the edges of the mantle along 
the margins of the valves. Besides disclosing the unmistakable an- 
atomical structure characteristic of Mya, there was found in the 
sections of the median region at the apex of the foot a median 
saccular depression which was undoubtedly the byssal gland with 
the thread in place or with remains of the secretion from which the 
byssal thread was formed. 
This discovery leaves no doubt as to the fact that this well- 
known mollusc is provided with a byssus during its early life. One 
series of sections in my possession, from a specimen ten millimetres 
long, shows the structure admirably. How much longer than usual 
