DISTRIBUTION OF FORAMINIFERA 21 



down as microspheric individuals. This is obviously a method of reproduction favour- 

 able to w^ider distribution than the asexual reproduction of the microspheric individual. 

 In this latter case the young organism is born in the proximity of the parent, forms a test, 

 and is thereafter dependent solely upon its own powers of movement. 



The megalospheric and microspheric forms can be found in a great many genera of 

 whose life history we know nothing, but it seems logical to suppose that a similar mode 

 of reproduction occurs in them, and perhaps in all Foraminifera. In such case the 

 zoospores will be at the mercy of currents. Of their viability, i.e. of the length of time 

 during which they survive if they fail to conjugate, we know absolutely nothing, but 

 presumably it would be only a short period of hours, or days at most. But if, like a 

 great many similar organisms, these zoospores have the power to pass into a resting-spore 

 condition, they might well be transported for long distances, in a living state. 



Wayland Vaughan (V. 1933, BROF) has recently published a very suggestive paper 

 in which he attempts to explain the migrations of the large Orbitoid Foraminifera 

 between Europe and America in Upper Cretaceous times by a zoospore theory. He 

 suggests that the zoospore stage was transported by currents and, given a viability 

 equal to that of the free-swimming larval stages of some corals, up to 30 days, would at 

 intervals across the Atlantic find banks and submarine peaks on which they could 

 develop into mature individuals before starting on a fresh stage of the voyage again as 

 zoospores. He concludes (p. 935, op. cit) "that the facts of the known geographic 

 distribution of the Orbitoid Foraminifera, during successive geological epochs, can be 

 accounted for by the transport of the organisms during larval stages by ocean currents, 

 and that the postulation of the former existence of extensive land areas where there are 

 now oceanic waters of abyssal depths is not necessary. The maximum required change 

 in the depths of the ocean would be that some of the sub-oceanic peaks and ridges should 

 have stood near sea level, but it is not certain that even such changes were necessary". 

 Wayland Vaughan points out that the unknown factor in the problem is the duration of 

 life of the zoospores, and does not invoke the aid of a resting-spore condition to prolong 

 the duration of life. 



With the data of submarine banks and peaks which he gives, his theory seems feasible 

 enough so far as the Atlantic is concerned. But I doubt whether it would be tenable as 

 regards the South Pacific, unless the viability of the zoospore were indefinitely extended 

 by a resting stage. Of the existence of such a condition I admit there is at present no 

 particle of evidence, but it seems not impossible, and I hope that the biological work 

 now being done at the La Jolla Institute by Mr Earl H. Myers (M. 1933, MTF) may 

 throw some light on this question. There is no problem connected with the Foraminifera 

 more puzzling, or of greater interest than the occurrence of well-defined species at great 

 distances from their original habitat, especially when, as frequently is the case, the 

 intervening territory is so well known that the presence of the organism could hardly 

 have been overlooked. Such an instance may be found in this report in the case of the 

 species renamed Botellina goesii (No. 132). 



