132 AVYVILLE THOMSON, ON SYNAPTA INII^ERENS. 



mentaiy, and even in the simplest and most minute embryos 

 there was not the slightest trace of larval appendages. 

 I am, therefore, inclined to believe, that no independently 

 organised pseudembryo is produced, but that the Echino- 

 derm is developed at once from a simple ciliated germ. I 

 shall not, however, consider my task completed, till this 

 point be fairly cleared up ; and, in the mean time, I merely 

 offer the present communication as a contribution to the 

 history of a limited period in the development of the young. 



The two most important memoirs on the structiu'c of the 

 genus Synapta are those of De Quatrefages (" Memoire sur 

 la Synapte de Duvernoy'^ ' Annales des Sciences Naturelles,' 

 1842), and of Johannes Miiller (' Ueber Synapta Digitata,^ 

 Berlin, 1852). Sijnapta Duvernaa (A. de Q.) must be 

 regarded as a synonym of the species under consideration, 

 and Miiller's observations refer to a closely allied form which 

 has been frequently met with on the English coast. 



I have had an opportunity of dissecting Synapta inhcerens 

 "vvith care, and as a general knowledge of the mature form is 

 necessary before we can understand fully the structure and 

 development of the young, I shall briefly abstract my own 

 results and those of previous observers, so far only as they bear 

 upon this point. 



Synapta inhcerens is provided even more richly than 

 S. digitata, with the remarkable ciliated trumpets described 

 by Miiller. 



I hope to have an opportunity of illustrating fully this 

 anomalous respiratory apparatus and the organs of repro- 

 duction in a future paper. It is unnecessary to allude to 

 them at present, as no trace of either system is perceptible in 

 the most advanced embryos which I have yet examined. For 

 more minute anatomical details I refer the reader to the 

 memoirs above cited, and for certain special points, to the 

 papers of Grube, Duben and Koren, Held, Ley dig, and 

 AVoodward. 



Synapta inh.ekens, O. F. Muller (sp.) 



Holothuria inhcerens, O. F. Miiller, Zool. Dan, taf. xxxi, 

 figs. 1 — 7. 



Chirodota pinnata, Grube, Aktinien, Echinodermen, &c., 

 p. 41. 



Synapta inlicerens, Rathke, Nov. Acta Nat. Cur. T. xx. 



Synapta Duvernaa, A. de Quatrefages, Ann. des Sc. Nat., 

 1842. 



Synapta inhtBrens, Woodward and Barrett, Free. Zool. 

 Soc. Lond., 1858, 



