414 Prof. H. James-Clark on the Anatomy and 
The other or posterior set of strie (l4, ) is much more 
readily detected than the anterior one, and the stri@ are about 
three times as numerous. They are so closely set together that 
it is a difficult matter to count them, although viewed with a 
one-eighth-of-an-inch objective. They extend, like those of the 
anterior set, over the whole breadth of the membrane, and, ter- 
minating abruptly at the peripheral margin (/', /*), give to the 
thickened edge a milled appearance. This milling is, moreover, 
rendered conspicuous by an incrassated, scalloped “border (7), in 
which the striz (/*) of the front set terminate*. The striated 
membrane is very flexible, and is frequently made to undulate, 
apparently by the successive impacts of the vibrating cilia. 
The apparently most important members of the adherent 
organ are the hooks (h). They vary in number from twenty- 
two to twenty-four, and curve in a direction which is diametri- 
cally opposite to the upward coil of the vibratory organ; 7. e. 
they are leotropic. They are separate pieces, of an £-formed 
(fig. 18, 4,4?) shape ; the upright part of the £ being the hook (h) 
proper, and the horizontal limb (43) the base of it. These £’s are 
arranged in a circle with their horizontal limbs all pointing one 
way—. e. the same as the upright part or hook—and nearly or 
quite touch each other, according to circumstances. A spur-like, 
slender point (4?) projects from the horizontal part, in the oppo- 
site direction, and is about half as long as the latter. Along 
this spur and the convex side of the hook a broad, lunate crest 
(k) arises, and, nearly filling the interval between two succeeding 
hooks, projects peripherally beyond the tips of the latter. This 
crest is excessively faint, and not recognizable as a distinct body 
unless the striated membrane is removed ; although it is to be 
If this be true, then the whole group of Vorticellidee (from which no one 
would for a moment think of separating Trichodina) must be removed to 
the class of Acalephe! We must, for own part, however, unequivocally 
dissent from this view, since it is quite at variance with our own observa- 
tions. But, again, according to another, more recent statement of Prof. 
Agassiz, in his ‘ Essay on Glnssiecabious (Boston, 1857, p. 72; London 
ed., 1859, p. 108), he has satisfied himself of the “propriety of uniting 
the Vorticellide with Bryozoa,” 7. e. the group of Vorticellide ; and con- 
sequently the Acalephan (vide preceding paragraph) Trichodina is Mol- 
lusean! From this view, also, we would modestly, but unequivocally, dis- 
sent, not only as the result of our own investigation, but in accordance 
with the observations of other very competent authorities. This view 
would also seem to argue that the Bryozoa—if they do not strictly belong, 
with Polypi, to the eS Radiata, as is insisted upon by other and 
eminent authority—are at least a transitional group between Radiata and 
Mollusca. 
* The separation of these two sets of strie, or radiating ridges, is an 
excellent test of the quality of a quarter-inch objective ; a one-eighth-of- 
an-inch lens can do it easily. 
