1897. NOTES AND COMMENTS. 375 



definite variation." It furnishes the dark-eyed varieties of Primula 

 Chinensis, and governs the variations in markings of marigold, poppies, 

 pelargoniums, and many others. A striking case is afforded by a 

 cultivated species of Coreopsis (C. tinctoria). This is a Composite 

 flower, the rays of which are yellow with a small but variable maroon 

 base. In the very numerous varieties the maroon constantly 

 encroaches upon the yellow, until, in extreme forms, it quite super- 

 sedes the body-colour. The impression given (though for some reason 

 this was not proved by sections) is that " the brownish pigments were 

 spread first over the upper surface and subsequently increased in 

 depth, first showing through in the thin areas." A similar series is 

 presented by the flowers oi2t.Freesia {F. refracta var. alba). In this case it 

 is the appearance and gradual spread of an orange-yellow over the 

 pure white that is claimed as an instance of definite variation. The 

 colour shows itself first at the base of the upper petals, and extends 

 over their inner surface, then appears on the backs of the petals, 

 following the same definite centrifugal lines as in Coreopsis tinctoria. 

 Sections made through petals from various flowers in the series showed 

 that the j'ellow pigment on its first appearance was confined to a 

 single layer of subepidermal cells, whence it extended through the 

 intermediate cells to the under surface. 



The facts are interesting enough, but, after all, they seem to have 

 but little bearing on the question of definite variation, except in so far 

 as they suggest that many supposed cases are the natural outcome of 

 physiological causes. It is not difficult to imagine a reason why 

 colour should spread in this centrifugal manner. It is doubtless in 

 some way connected with nutrition, and as the petals are attached to 

 the floral axis by their bases, a change might be expected to start at, 

 and spread from, the point most nearly connected with the main axis 

 from which the member receives its supply of nourishment. 



Boulder Clay, a Marine Deposit. 



In 1843 Portlock recorded the occurrence of shells in the Boulder 

 Clay of the N. of Ireland, and stated that it was a marine sedimentary 

 deposit. In 1879-80, S. D. Stewart published a list of no less than 

 sixty-nine species of Mollusca from the Boulder-Clay of the N.E. of 

 Ireland, and remarked on the occurrence of fragile forms, as Leda 

 pygmaa and L. minuta, with united valves, as indicating that these 

 shells had lived and died in the position in which the}' were found. 

 Joseph Wright and James Neilson have now systematically recorded 

 the Foraminifera found by them in Ireland and around Glasgow in 

 the Boulder Clay, and thus give additional evidence as to the marine 

 sedimentary nature of this deposit. According to these authors 

 (Trans. Geol. Soc. Glasgow, X., 263-279), the Foraminifera found therein 

 are exceedingly abundant in places, are mainly boreal forms, and are 

 as perfectly preserved as are those of a recent sounding. Messrs. 



