84 Miscelianeous. 
the development of one species have been shortened? M. Giard 
communicates no observations which might prove the impossibility 
of such a shortening of the development. Consequently I maintain 
my view that the species described since by Dr. Russmann under 
the name of Z’hompsonia globosa (Verhandl. d. phys.-med. Gesellsch. 
zu Wirzburg, 1872, oder Arbeiten aus dem zoologisch-zootomischen 
Institut zu Wurzburg, Band i. p. 131), after my drawings and spe- 
cimens, has larvee which leave the egg only in the Cypridine form. 
There is even no stringent reason to take it for granted, as M. Giard 
not very judiciously seems to do, that they undergo a conspicuous 
change of form within the egg, although this, of course, remains to 
be ascertained. Yours very truly, 
Wiirzburg, November 20, 1874. Prof. C. Semper. 
On the Circulatory Apparatus of the Echinida. By M. E. PEerrrer. 
The circulatory apparatus of the Sea-Urchins has been the subject 
of numerous investigations, which are summarized in Valentin’s 
monograph on Echinus lividus, and more recently in the fine mono- 
graph of the Echinida by Mr. Alexander Agassiz. These various 
researches have left very doubtful even the most important points in 
the arrangement of the vascular apparatus. We can regard as certain 
only these two facts :—1. The existence of an intestinal vascular appa- 
ratus. 2. The existence of a system of vessels communicating with the 
ambulacral canals, and usually designated by the name of the aquiferous 
apparatus. We did not even know whether these two systems of 
vessels were distinct, or whether they communicated with each other. 
This communication, imperfectly seen by Louis Agassiz, and since 
sought in vain by many anatomists, has only been met with again 
quite recently by Hoffmann in the Spatangi and Towopneustes, be- 
longing to the regular Echinida. But there were still many ques- 
tions to be solved :—The mode of vascularization of the test indicated 
by some authors seemed very doubtful. The structure of the heart, 
or at least of the organ so called by anatomists, remained very 
obscure ; moreover there was occasion, in the presence of contradic- 
tory statements, to verify the announced results, to group and coordi- 
nate, and finally to present a complete and homogeneous description 
of the circulatory apparatus of the Echinida. 
This is the problem which I have endeavoured to solve during a 
stay of several weeks at the laboratory of experimental zoology of 
M. de Lacaze-Duthiers at Roscoff (Finisterre). 
The dredging-operations instituted by M. de Lacaze-Duthiers at 
his laboratory brought in every day with certainty a great number 
of specimens of Echinus sphera, which, in consequence of their con- 
siderable size, were particularly well adapted for my investigations, 
the results of which may be summarized as follows :— 
Beneath the madreporic plate a canal (the sand-canal) originates, 
which descends vertically towards the lantern, passing along the ceso- 
phagustotheleftand behind. This vesseland the cesophagus are united 
by a mesenteric lamina which embraces the organ hitherto known 
