204 CARNEGIE INSTITUTION OF WASHINGTON. 



Investigations on the Specific Characters of Marine Amcebas at Tortugas, 



by A. A. Schaejfer. 



This investigation on marine amoebas was prompted by the fact that there 

 is an ahiiost total lack of information concerning these organisms, both from 

 the systematic and from the experimental point of view. During May and 

 June 1919, 5 new species were isolated and described from the v/aters in the 

 neighborhood of Tortugas, Florida, and an equal number of species were found 

 whose specific descriptions are still, for one reason or another, incomplete. 

 Further data on these amoebas will be published later. 



The amoebas were obtained in the following ways: (1) By to wings of the 

 surface-water in the vicinity of Loggerhead Key, especially in shallow water. 

 A small number of individuals of several species were always found in these 

 towings. (2) By washing floating and submerged seaweeds {Sargassum, 

 Halimeda) and eel-grass. The sediment from these washings always yielded a 

 considerable number of amoebas of various species. Sargassum brought to 

 the shore by a southeast gale of several days' duration carried one large 

 species of amoeba which was not found under other circumstances. (3) By 

 cultures in glass dishes made up of sargassum and other seaweeds and eel- 

 grass, with or without a small quantity of finely ground timothy hay, and 

 normal sea-water. Through some of these cultures a very slow stream of 

 water was kept running. Some of the dishes were covered to prevent evapor- 

 ation, while others were left uncovered. Certain species grew very readily in 

 these cultures. (4) By filtering a slow stream of sea-water through cheese- 

 cloth holding a small wad of cotton. This method yielded the largest variety 

 of species, but the number of individuals of any species was small. 



Excepting the fact that contractile vacuoles are lacking in marine amoebas, 

 these organisms do not differ in their general characteristics from fresh-water 

 amcebas. Some of the marine amoebas possess actoplasmic ridges such as are 

 found in the fresh-water Amoeba verrucosa and its congeners. Vacuoles in 

 large number are often seen in marine amoebas, and in rare instances a vacuole 

 may be observed to disappear slowly. But such cases of disappearance are 

 probably not to be interpreted as physiologically similar to the functioning of 

 a contractile vacuole. The general characters associated with streaming — 

 pseudopod formation, rate of movement, formation of food-cups, and so forth — 

 are similar in both fresh and salt-water amcebas. 



It is especially worth noting that during active locomotion the outer or 

 surface la^^er of the marine amoebas moves forward over the ectoplasm in the 

 same way as the surface layer of fresh-water amoebas is observed to do. It is 

 also of importance to know, especially from the point of view of systematics, 

 that optically active crystals occur in some species of amoebas Uving in the 

 sea, for, as I have shown in previous papers, the crystals form one of the most 

 constant and dependable characters known to these organisms. Unfortun- 

 ately for systematics, less than half of the number of marine species thus far 

 described possess crystals. It is perhaps worth noting, also, that endoplasmic 

 inclusions of all sorts — vacuoles, nucleus, protoplasmic granules, etc. — are 

 much less conspicuous in salt-water amoebas than in those living in fresh water; 

 but this difference is due undoubtedly to the purely physical effect of the salt- 

 content of the water, for when marine amoebas are placed in fresh water, these 

 inclusions become more refractive to light and consequently more conspicuous. 



One of the chief objects of this investigation is to learn something of the 

 distribution of marine amoebas in the waters of the earth and of the factors 

 which control such putative distribution. This being the first recorded at- 

 tempt in the investigation of this problem, such data as have been obtained on 

 this point become of importance, however, only when compared with similar 



