166 CARNEGIE INSTITUTION OF WASHINGTON. 



It is the intention to follow up this study of the quantitative distribution 

 of amebas, if possible, with another study of the distribution of amebas 

 on the sea-floor down to several hundred fathoms, in the same general region. 

 The ultimate object is to secure as adequate an idea as possible of the quanti- 

 tative distribution of amebas in the Gulf Stream. It is believed that such 

 data would be of interest not only to students of amebas, but to biologists 

 generally, for we have no such data now regarding any of the lower animals. 



Observations on New and Imperfectly Known Species of Amebas. 



Two new species of amebas were found. One of them belongs to the 

 genus Pontifex and was found in considerable numbers in cultures made up 

 from floating algae, in the concrete tanks (see below), and in the tidal pool 

 on Sand Key (Tortugas). This species is large and conspicuous and it is 

 safe to say that it was not present in the waters of Tortugas in the seasons 

 of 1919, 1921, and 1922, for daily observation of numerous cultures during 

 these seasons revealed none of them. The species is very interesting from 

 several points of view but a full description of it must be deferred until later. 



The other new species is very small but of very distinctive shape and 

 behavior. It came up in considerable numbers in the concrete tanks and in 

 several of the cultures made up from floating algae. A full description will be 

 published later. 



A large number of Gibbodiscus gemma, which was described from a few 

 individuals in 1921 at Tortugas, came up in the tidal pool in Sand Key 

 (see below). They conformed to type, but there was considerable variation 

 in the presence and size of cubical crystals, and the shape during locomotion 

 is more often roughly circular or oval with the broad side advancing, rather 

 than oval with the narrow side advancing as previously described. A revised 

 description will be published later. 



In addition to the two new species mentioned above, representatives of the 

 following 14 previously described species were seen in the course of examina- 

 tion of the various mass cultures set up during the season : Mayorella conipes, 

 M. crystallus, Flabellula mira, F. citata, Thecamoeba rugosa, T. orbis, T. hilla, 

 Trichamoeba sphcerarum, Vexillifera aurea, Hyalodiscus fulvus, Dactylo- 

 sphcerium acuum, Pontifex maximus, P. minimus, Gibbodiscus gemma, and 

 Rugipes vivax. The present season was, therefore, more favorable to growth 

 of amebas than last season, when only 8 species not previously described were 

 seen. Altogether 29 new species have now been described from Tortugas. 



A tidal pool was discovered in the middle of Sand Key (Tortugas) with 

 considerable quantities of green and brown algae in it. The bottom was in 

 fact entirely covered with algae. At low tide there was about 20 cm. of 

 water in the pool at the deepest part, and the pool was about 4 meters in 

 diameter. At high water the pool was about 8 by 10 meters in extent. The 

 following 7 species of amebas were found in it : Thecamoeba rugosa, T. orbis, 

 Mayorella conipes in large numbers, Vexillifera aurea, Gibbodiscus gemma in 

 large numbers, Pontifex horridus (new species) in large numbers, and Tricha- 

 moeba sphcerarum. Sand Key had not been visited for several years and it 

 is therefore impossible to say how long the tidal pool has existed there. 

 Its value as an aid in studying distribution is at once recognized. A some- 

 what similar but smaller pool was blasted into East Key in the hope that a 

 natural culture for amebas will form there. 



