432 General Notes. [April, 
posed morphological identity of the two, if the time of their 
appearance is the only index of homology in Echinoderm larval 
appendages. The comparative anatomy of the rods of the body 
of the pluteus seems to me to point without doubt to an homol- 
ogy of the lateral arms of Ophiuran larval and the apical rods of 
Arbacia. All the appendages of the various forms of Echino- 
derm larvæ may be regarded as specially, er perhaps independ- 
ently acquired structures, which are destitute of any great value, 
comparatively speaking, as far as the phylogeny of the Echino- 
derms is concerned. If I am right in looking at them in this 
way, the stages of growth in which the larva of Arbacia and the 
Ophiuran was, when on the one hand an apical 1 pair of rods, and 
on the other the lateral arms appear, need not coincide an yet 
the two may be homologically the same.—/. Walter Fewkes, 
PLATEAU’S RESEARCHES ON THE ABSOLUTE FORCE OF THE MUS 
CLES OF Bivatves2—The great apparent force of the adductor 
muscles of lamellibranch mollusks is a fact universally knows, 
and which forms the basis of La Fontaine’s fable of the rat an 
the oyster. Fishermen and naturalists have made this the sub- 
ject of interesting remark. Thus Darwin, speaking of the gren 
Tridacnas of tropical seas, says, that any one imprudent enous. 
to introduce his hand between their valves, would be unable to 
withdraw it while the animal lived. Léon Vaillant relates that 
the divers whom he employed at Suez, and who procured 
B 
hi 
specimens of Tridacna elongata, advised him not to touch thes 
animals on the side of the opening of the shell. ‘ments 
Plateau then adds: “ I myself, in the course of erperimet 
related in this notice, have been witness, whenever I wished y 
Mya arenaria, of a fact at first sight very surprising; i a 
living mollusk we break, with the aid of a knife or pie 
small area of the shell in the neighborhood of the hinge, age 
ing noise is heard, and we see the valves open and od 
gether with a loud noise under the influence of the traction i 
adductor muscles.” ded 
Darwin’s observations on the transportation of Unio gee 
by its closed valves to a duck’s foot ; of a Cyclas fixed in the Si 
way to the foot of a water-beetle (Dytiscus), and of Cycle’. 
itself to the foot of a triton so as to amputate it, are a 
aad it eaking te f the observations of others who submits 
adductor muscles to experiment. i ' 
Noticing A, oggy ọn the elongatio®®, Vail 
which the adductor muscles of Anodonta; those T teral rods © 
1 From what has aid it is t the name c3 bent 
designate re appendage eis irasogses a be ODD 
as long been used. - Prem. Par. 
_, _ Recherches sur la force absolue des muscles des invertebrates. Par M. Pro 
orce absolue des les adduct des mollusques Lamellibranches. Belgiqn® ™ 
fessor Felix Plateau. Extrait du Bulletins de l’ Academie royale de 
1883, 8vo, pp. 36. 
