ARTIFICIAL CLILTURK OF MARINE PLANKTON ORGANISMS. 425 



and h c.c. of a 1'5 per cent, solution oF anhydrons sodium 

 carbonate. A tew Calanus fi umarchicus and some decapod 

 Zceas Avere put in, together witli a quantity of a culture 

 containing mixed diatoms. On September 8t1i all the Zoeas 

 were dead, but three Calanus were alive, and Nitzschia 

 and a number of bottom diatoms were very plentiful. On 

 September 17th the three large Calanus were alive and 

 vigorous, and a considerable number of Nauplii were seen 

 in the flask. By September 22ud two of the Nauplii had 

 developed into yonng Calanus. These, howevei-, did not 

 live for more than a week or ten days, and the adults also 

 died. The flask was abandoned on November loth, the 

 water in it not havino- been chano-ed since the commencement 

 of the experiment. 



Echinus hybrid. — A successful experiment on crossing 

 E. esculentus and E. acutus was carried out by Mr. 

 W. De Morgau, who was working at the Plymouth Laboratory. 

 We provided him with treated water and diatom cultures for 

 food, and he followed our methods. We are indebted to him 

 for allowing us to publish these results. Some eggs from a 

 ripe E. esculentus were fertilised by active sperm from an 

 E. acutus, in sterilised water, on March 29th, 1909. Healthy 

 larvae were obtained, and were transferred two days later to 

 tank- water, which had been treated with animal clnu'coal and 

 filtered through a Berkefeld filter. A culture of Nitzschia 

 closterium var. was added as food, and the larvie developed 

 rapidly, feeding well. Several were completely metamor- 

 phosed on May 7th, or thirty-nine days after fertilisation. 

 In all thirty young hybrids were obtained, and a number of 

 these are still alive and feeding, on red weeds. 



Sacculina carcini. — Mr. Greoffrey Smith has recorded 

 the fact ('Quart.. Jonrn. Micr. Sci.,' vol. 51, 1907, p. 625) 

 that he was able to rear the larvae of Sacculina up to the 

 Cypris stage, when they attached themselves to their host, 

 Carcinus msenas. These larvae were kept in aquarium 

 tank-water ti'eated with animal charcoal and filtered through 

 a Berkefeld filter. In this case the question of , food did not 



