368 PROGRESS OF MICROSCOPICAL SCIENCE. [^TnSk^u^^im} 
pair of longer hooks, recalling to mind the arms of an anchor. The 
spicules bear a near resemblance to those at the lower extremity of 
Euplectella, but have only two instead of four hooks at the end. In 
the specimen but few of the spicules present the complete character as 
described, most of them apparently having been broken. The object 
of the tufts of spicules, with their recurved prickles and anchor-like 
free extremities, in Pheronema would appear to be to maintain the 
position or preserve the anchorage of the sponge in its ocean home, 
and perhaps in the living animal they are incessantly produced as 
occasion may require, just as a Mytilus or a Pinna renews and attaches 
its threads of byssus to secure its position. The siliceous spicules of 
Pheronema are composed, as in sponges generally, of concentric layers, 
and exhibited a delicate tubular axis. A spicula from one of the tufts 
measured as follows : — Spread of the anchor, one-tenth of a line ; 
shank of the anchor, one-thirtieth of a line ; prickled portion of shaft, 
one-fortieth of a line ; shaft where thickest and without prickles, one- 
eighteenth of a line, thinning out to the inserted end, where it was not 
more than l-300th of a line. 
The Structure of the Cotyledon in Monocotyledons. — This subject has 
occasioned some controversy between the two eminent botanists MM. 
Van Tieghem and Lestiboudois, who have been fighting out the ques- 
tion in a series of papers before the French Academy. We must 
confess that the rival debaters have not put their respective opinions 
forward with that degree of clearness which is desirable. But so far 
as we can gather the meaning of the discussion, the question stands 
thus : — M. Van Tieghem holds that, in Monocotyledons as well as in 
Dicotyledons, the cotyledon generally receives, as do the other leaves, 
an odd number of bundles, and that its symmetry, and consequently 
that of all its appendages, is the same in the two divisions. The 
number of cotyledonary bundles is smaller than that of the primitive 
vascular planes, which in the central body of the root alternate with 
as many other bundles, and the median nervure corresponds to one 
of these primitive vascular bundles. A subsequent note by M. Lesti- 
boudois implies that he too, holds this opinion, and that the view con- 
tested by M. Van Tieghem was that which he considered applicable to 
the primordial and not to the secondary leaves of the Monocotyledon. 
— See ' Comptes Eendus,' April 26th and May 3rd. 
The Lymphatics of the Epithelium. — A paper of much importance, 
since it shows us the danger of accepting the appearances produced in 
tissues by means of reagents, as representing the living condition, was 
sent in to the French Academy of Sciences by M. Eobinski, at a 
recent meeting (April). Alluding to M. Recklinghausen's use of 
nitrate of silver to stain the tissues, he says, that he has seen how the 
pseudo-lymphatics are formed in the epithelium by this salt. " The 
lines of demarcation," he says, " of the epithelium cells are always 
stained a deep brown colour, while the middle of the cell is seldom 
coloured, owing to the fact that the colour has to pass from the margin 
towards the centre. It happens thus, that while the whole preparation 
is more or less brown, that certain cells are unstained. According to 
