84 MtsceUaneous. 



the development of one species hnve been shortened ? M. Giard 

 eomraunic.ites no observations which might prove the impossibility 

 of such a shortening of the development. Conseciuently 1 maintain 

 my view that the species described since by Dr. Kussmann under 

 the name of Thompsonia nJobosa (S'cvhanAl. d. ])hys.-nied. (Jesellsch. 

 zu Wiirzburg, 1S72, oder Arbeiten aus dera zoologisch-zootomischen 

 Institut zu Wiirzburg, liand i. p. VM), after my drawings and spe- 

 cimens, has larvK 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, 



Wurzburg, November 20, 1874. Trof. C. Semper. 



On the Cirndatort/ Apparatus of the Echinida. By M. E. Perrieb. 



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. AVe did not even know whether these two systems of 

 vessels were distinct, or whether they communicated wdth 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 Spaiancji and Toxopneustfs, be- 

 longing to the regular Echinida. But there were still many ques- 

 tions to be solved : — The mode of vascularization of the test indicated 

 bv 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-Diithiers at lloscoff (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 sphara, which, in consequence of their con- 

 siderable size, were particularly well adapted for ray 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 oeso- 

 phagus to the left and behind. Thisvesseland the oesophagus are united 

 by a meseuteiic lamina which embraces the organ hitherto known 



