162 Proceedings of the Royal Irish Academy. 



'iv) There is a fourth form of variation which has been familiar to. us for a 

 long time, but which does not appear to liave been definitely recognized, 

 although scanty references to it may be found in the literature of the group. 

 This is the occurrence of both giant and pygmy forms of species having 

 normally a definite range of size, and without environmental conditions, such 

 as superabundance or deficiency of food supply, etc., to explain the variation. 

 It may be granted that pygmy forms are likely to escape observation, or, if 

 seen, to be regarded as immature, while giant forms are likely to attmct 

 observation. Cornvspira strioluta Brady, in the deep cold water of the Faroe 

 Channel at a temperature of -lO-i'C , attains a size of over an inch in diameter, 

 whilst in other gatherings from various parts of the world it does not reach 

 a quarter of that size." Tcchnilella hijitmtn Norman occurs in some numbers 

 in one of Earland's dredgings off St. Kilda in 1.448 metres. The majority of 

 the species are normal, about y, inch long, but fragments greatly exceeding 

 that size also occur, which show that the perfect shells must have been quite 

 1 inch in length. There is little doubt that the lai-ge coarse variety 

 Haptophraginium erassimargo Norman, is a giant form of the normal H. 

 caiuiricme (d'Orb.), but in this case the giant variety either replaces the 

 type, or, when both are present, is as common as the normal." 



Many other instances of gigantism could be quoted, but they are as a rule 

 baseil on single records, and the phenomenon will require a good deal of 

 careful study before its exact meaning will be discovered. 



The evidence in support of nanism, of the existence of pygmy forms, is 

 very slight, apart from one particular example, with which we shall deal at 

 some length. We have observed such pygmies in CristeUaria crepidula 

 (F. and M.j, and a few otlier species, but they are ditticult to separate from 

 young and immature specimens. The exceptional instance is the pygmy 

 form of Vfrtuuilitm polystropha (Reuss), figured and recorded by us from the 

 West of Ireland in 1913," and subsequently identified from several widely 

 separated localities. We were at first inclined to regard this as the 

 microspheric form of the species, but our subsequent researches have proved 

 it to be an adult pygmy form, showing all the modifications of the normal 

 shell of the species. To these we sliall refer in greater detail when dealing 

 with the s[>ecie3 Vtnifuilina pohjstropha. 



The biological significance of this phenomenon of gigantism and nanism 

 is, in the present state of our knowledge of cytological bionomics, extremely 



*" Described and illastnUed by us in J. R. Micr. Soc., 1913, pp. 274-5, 6g. 36. 

 *• Describt.'d and illustrated by us in '■ Knnwledge," vol. xxxiii, Xo. 508, Ifov., 1910, 

 pp. 422-425, tigs. 2. 3, 4. 



*' Loc. c'U. (note 7), pp. 95-56. 



