DEPARTMENT OF MARINE BIOLOGY. 201 



Cages No. 45 and No. 46 are of the same size as those last mentioned. 

 In cage 45 we placed 183 young of Cerion incanum from Key West, in order to 

 determine what percentage of these will reach maturity. In cage 46 we placed 

 an abnormal specimen of Cerion viaregis. This had a spiral keel, which may 

 be the result of an injury, although I was unable to discover any sign of it. 

 With it I also placed a normal specimen of Cerion viaregis in order to determine 

 if this character might be transmitted to offspring. 



In addition to these, five groups of cages were made which have the same 

 size as the four unit cages, but they have only one partition in the middle, 

 thus making them 3 by 6 feet and 3 feet high. In these we placed the fol- 

 lowing combinations : 



No. 47. 25 each of Cerion incanum and Cerion viaregis. 



No. 48. 25 each of Cerion incanum and Cerion casablanccp.. 



No. 49. 25 each of Cerion incanum and Cerion uva. 



No. 50. 25 each of Cerion incanum and Cerion crassilabris. 



No. 51. 25 each of Cerion viaregis and Cerion uva. 



No. 52. 25 each of Cerion viaregis and Cerion crasbilabris. 



No. 53. 25 each of Cerion casablancoe and Cerion uva. 



No. 54. 25 each of Cerion casablancce and Cerion crassilabris 



No. 55. 25 each of Cerion uva and Cerion crassilabris. 



In cage 56 I placed 203 young of various sizes of the huge new form collected 

 in Middle Bight, Andros, which I have called Cerion mayori. 



Two additional species were introduced this year on Loggerhead Key, 

 one Cerion mayori, as above stated, and the second, Cerion incanum, as also 

 stated above, but of this species we also placed a large colony about the water 

 tower at the northern end of the island, in order to have additional material 

 if we should need it for breeding purposes in the future. 



Investigation on Marine Amoebas at Tortugas, Florida, by Asa A. Schaeffer. 



The work on amoebas during June and July 1921, at Tortugas, Florida, was 

 a continuation of work begun there in 1919. The greater part of the time was 

 devoted to a system-atic study of marine amcebas. All the species discovered 

 in this locality in 1919 were found again this year, and 16 new species were 

 discovered and described. Several more species were found whose descrip- 

 tions, for one reason or another, remain incomplete. More species have been 

 reported from this station than from all other marine stations together. 

 The observations on the systematics and distribution of marine amcebas have 

 advanced far enough to warrant the following tentative conclusions : 



(1) The sea is probably richer in species of amoebas than fresh water. 

 The number of species in existence is very much larger than is commonly 

 thought. Judging bj^ the number reported from time to time in both fresh 

 and salt water, amoebas seem to be as numerous in species as, for example, the 

 Foraminifera. 



(2) Marine amcebas are distinct from fresh-water species. No species has 

 yet been found living and reproducing in both fresh and salt water. 



(3) The average size of fresh-water amoebas is larger than that of marine 

 amcebas. 



(4) The most important factor affecting the distribution of amoebas is the 

 food-supply, A few species live on bacteria, but the majority live on diatoms 

 and other algse. It follows, therefore, that the largest number of species 

 and individuals are found where diatoms abound. 



(5) Other important conditions affect distribution, for some species occur 

 in great numbers in natural and artificial cultures, while comparatively few 



