ON THE DEVELOPMENT OF SOME BRITISH ECHINODERMS. 9 



that it belongs to L. ciliaris. It is, however, still very desirable that 

 this larva should be reared to metamorphosis — and as it has now been 

 fomid to be easily reared, this will probably soon be done — this large, 

 beautiful larva must, indeed, be a magnificent object for embryological 

 study. 



In the Echinodermenlarven der Plankton Expedition (pp. 39-40), I have 

 remarked, in connection with the suggestion made by Hensen that the 

 voung larvae might be fixed, that this conclusion is scarcely justified, 

 because the young larvae have not yet been found. To this remark 

 Hensen has added the following note (p. 40) : " Meine ^usserung 

 lautet : ' Die I. Fahrt brachte 114, die II. 11, und die III. 78 Luidien mit 

 Stern, in Summa 203, deren Diagnose wir Hrn. Mortensen verdanken. 

 Es miissen doch wohl die jiingeren Larven eine festsitzende Lebensweise 

 haben, sonst konnten sie uns nicht entgangen sein.' Da Zahlen beweisen, 

 muss ich an diesem Satz festhalten." Though I have always been quite 

 convinced that the Luidia larva could not have a fixed stage before the 

 free-swimming larval stage, it is quite satisfactory for me that I have 

 now been able to give the definite proof that my opinion, founded on 

 morphological grounds, was right, in spite of Hensen's statistics. To 

 be sure, my observations are made on L. ciliaris, while Hensen speaks 

 of L. sarsi : but to suppose that of two so very similar larvse one 

 should be fixed in its first stages, the other free-swimming, would really 

 be too absurd. 



It is very remarkable that the larvae of L. ciliaris appear to be com- 

 paratively rare at Plymouth. Being impressed with the enormous 

 development of the gonads in this species I have tried to make an approxi- 

 mate calculation of the number of eggs in a large L. ciliaris. In a specimen 

 of 30 cm. arm length I counted the number of gonads — which are here 

 arranged in a series along each side almost to the point of the arm in- 

 stead of one large gonad at each side of the basis of the arm as is the rule 

 in Asteroids— and found them to number 150 in each series — 300 per arm. 

 As the species is seven-rayed, a complete* female of that size, which is 

 nearly the average, has 2,100 ovaries ; these are, however, of some- 

 what different size, decreasing in size towards the point of the arm. 

 An ovary from about the middle of the arm was divided into a 

 hundred parts of as nearly as possible equal size, and the number 

 of eggs in one part was counted ; it was ca. 3,000. This means 

 that in one ovary there are at least ca. 300,000 eggs, probably nearer 



* The arms very easily break off, ami it is quite difficult to get complete specimens, 

 though such are ofteu seen in the contents of the trawl, before it is hauleil on deck. 



