24 EMBRYOLOGY OF THE STARFISH. Part I. 



the odd brachiolar arm, the pair of small brachiolar arms having no such appendages. 

 It has been found convenient to retain for these peculiar arms the name of brachi- 

 olar, used by Miiller to distinguish one of his genera (Brachiolaria) of Echinoderm 

 larvae. I have not succeeded in ascertaining the functions of the disks; the termi- 

 nal buttons undoubtedly are used in the last stages of growth of the larva as 

 supports, by means of which they can attach themselves, while the young Starfish is 

 resorbing the larva; for during that process the larvae never float about, but inva- 

 riably sink to the bottom of the jar in which they are kept, and remain attached, 

 apparently by means of the brachiolar arms, during the resorption of the larval 

 appendages. 



These larvae are found floating in large numbers at night near the surface, among 

 cast-off skins of barnacles, furnishing them with food during the time when they 

 swim freely about, in company with multitudes of small Crustacea, Annelids, and 

 Hydroids. They seem to be nocturnal, as I have only found here and there single 

 specimens", when fishing for them under exactly the same circumstances of tide and 

 wind, during the day-time. 



