260 Miscellaneous. 
middle, or only in the outer fourth ; and we may explain, by a similar 
division taking place at the level of the disk, the numerous cases of 
Ahexamelism, in which, except in the number of rays, we find nothing 
abnormal in the constitution of the starfish. 
But this is not always the case. Ihave long since expressed the 
opinion that the radial symmetry of the Echinoderms is only appa- 
rent, and that the antimera of those animals are arranged in ac- 
cordance with a quincuncial spiral, in such a fashion that an urchin 
or a starfish may be compared, from the point of view of general 
morphology, not to a regular corolla, but to those flowers which are 
symmetrical with respect to a plane, such as those of the Papiliona- 
cee or Labiate. In the latter, in fact, there exists a combination 
of bilateral symmetry and of the spiral arrangement which we also 
meet with in the Echinoderms. Starting from this notion I wished 
to see whether the anal glands of Asteracanthion rubens had not the 
same morphological value as one of the pairs of hepatic ceca. For 
this purpose I opened a certain number of specimens with six arms, 
and saw, with surprise, that several of them presented two sand- 
canals terminating at a single madreporic plate, which, however, 
was formed by the union of two plates. Consequently I had before 
me true double monsters. Couch, the excellent author of the 
‘ Fauna of Cornwall,’ has described* a specimen of A. rubens (which, 
following Fleming, he calls A. glacialis), possessing eight rays. 
This individual presented three madreporic plates, forming the three 
angles of a triangle inscribed between the bases of four rays; the 
four other rays were outside this triangle. This specimen was 
therefore a triple monster, evidently of rarer occurrence than the 
double monsters of which we have just been speaking, but perfectly 
analogous to them. 
From the preceding statement it follows that the examples of 
Asteracanthion rubens possessing more than five arms may be likened 
sometimes to the ccenobia of Botryllus, in which the number of 
unities constituting the ccenobium yaries from one cormus to 
another, and sometimes in the same cormus ; and sometimes to the 
compound coenobia of the genera Amarecium and Polyclinum. In 
other words, they are sometimes double monsters, sometimes simple 
cases of polymelism. It isremarkable that these two distinct cases, 
presented in a teratological form in <Asteracanthion rubens, also 
exist in the normal state in the group of Echinoderms. The So- 
lasters, for example, have a variable number of arms, but only a 
single sand-canal; while some examples of Ophiactis have several 
sand-canals, and are even capable of multiplying by a spontaneous 
scission of their compound ccenobium into several independent 
colonies.— Comptes Rendus, November 19, 1877, p. 973. 
On the Feeding of Dinameeba. 
Prof. Leidy remarked that bias frequently proved to be an obsta- 
cle in the way of research. In his study of the Rhizopods he had 
repeatedly watched different kinds of Ameba for long periods with 
* Mag. Nat. Hist. 2nd ser. no. 27. 
