362 



K. J. AliLKN AND M. VV. NKI.SON. 



PAGE 



Avtificiiil Sea- water . . . ; 393 



Alkalinity ..... 395 

 Salinity . . . . .402 



Light ..... 403 



Temperature .... 404 



Ge7iei-al Conelufiions .... 405 

 II. Mixed Cultures . . . . .407 



III. Notes on Particular Species of Diatoms, on their Methods 



of Reproduction, and on otlier Algae occumng in 

 Cultures . . . . .412 



IV. Rearing of Marine Larvae . . . .417 



Methods . . . . .417 



Echinus acutus .... 419 



E. esculentus ..... 420 



E. niiliaris ..... 421 



Cucuinaria saxicola .... 422 



Poniatoceros triqueter . . . 422 



Chsetopterus variopedatus . . 423 



Sabellaria alveolata .... 423 



Archidoris tuherciilata . , . 423 



Calanus finniarchicus . . . . 424 



Echinus hybrid ..... 425 



Sacciilina carcini .... 425 



Sunuuary of Metliod for Rearing Larva? . . 426 

 Bihliography . . . . . .427 



Introduction. 



The observations to be recorded in this paper were com- 

 menced in March, 1905. Tliey originated in an attempt to 

 find a general method for rearins: marine larval forms. 

 Several investigators had previously succeeded in rearing 

 eohinoderms, molKiscs, and poljchtetes fi'ora artificially 

 fertilised eggs, under laboratory conditions, but the process 

 was generally difficult and the results more or less uncertain. 

 The most promising method seemed to be that adopted by 

 Cnswell Grave (26), who was able to rear his larva3 by feed- 

 ing them on diatoms. Grave obtained his diatoms by placing 

 sand, collected from the sea bottom, in aquaria, and using 

 such diatoms as developed from this material. All the 

 uiethods, however, suffered from the uncertainty of not 



