44 



NATURE 



\_Nov. 20, 187^ 



sophical Transactions for 1857 ; but many other papers of 

 the same thorough and original character proceeded from 

 his pen. Amongst them will be remembered the fol- 

 lowing: — " On the Olfactory Apparatus in the BuUidse" 

 (1852) ; " On the Nervous Systems of Oiniiiastrephes 

 todarus" (1852) ; " On the Anatomy and Physiology of 

 the Dibranchiate Cephalopoda" (1S61) ; "On the Struc- 

 ture and Homologies of the Renal Organ in the Nudi- 

 branchiate MoUusca" (1S63) ; "On the Anatomy of 

 Doridopsis" (1865) ; "On the Anatomy and Physiology 

 of the Tunicata" (1S67). 



For some years previous to his death Mr. Hancock had 

 devoted much attention to the fish of the Carboniferous 

 period, and in conjunction firstly with Mr. T. Atthey, 

 whose fine collection afforded ample material for the pur- 

 pose, and subsequently with Mr. Howse, published a series 

 of fifteen papers on these coal-measure fossils. 



The promised Monograph of the British Tunicata, 

 preparations for which had made some progress even 

 before the death of Mr. Alder, had occupied much of his 

 time ; and though probably still unfinished, it may be 

 hopeti that the results of his investigations are so far 

 complete in themselves, th it the work, as far as it has 

 gone, may be saved to science. A supplement to the 

 Monograph of Nudibranchiate MoUusca had been a 

 matter long on his miud, but one that he had never been 

 able to devote himself to realising, beyond the collection 

 of materials. 



Allusion has been made to Mr. Alder, Mr. Atthey, and 

 Mr. Howse, as having been associated with Mr. Hancock 

 in certain of his papers ; to these must be added the 

 names of Dr. Embleton and the Rev. A. M. Norman as 

 occasional colleagues. 



On the establishment of the Natural History Society 

 of Northumberland, Durham, and Newcasde-upon-Tyne 

 in 1829, .Mr. Hancock became an active supporter, and 

 was one of the original staff of honorary curators ; 

 and on the formation of the Tyneside Naturalists' Field 

 Club in 1846, he was one of its principal and most influ- 

 ential promoters. When the new College of Physical 

 Science in Newcastle was instituted, his name, almost as a 

 matter of course, was placed on the provisional committee ; 

 and it was only when this body had completed its labours 

 and gave place to a permanent board, that he was per- 

 mitted, on the ground of ill-health, to retire from active 

 service in connection with the institution. He was a 

 Fellow of the Linnean Society, a corresponding-member 

 of the Zoological Society of London, an honorary mem- 

 ber of the Imperial Botanico- Zoological Society of Vienna, 

 and perhaps of some other similar bodies ; but honours 

 of this sort, though valued in their way, were thrust upon 

 him rather than sought. Though living a retired hfe, no 

 man more highly prized social intercourse. His kindly 

 helping hand was held out to every yoang naturalist : 

 Such were always welcome at his house ; and when ap- 

 pealed to by them, as was often the case, he made their 

 difficulties his own till he could help to solve them. 



It is yet too soon to attempt to shake oneself free from 

 a sense of his presence, or to essay to weigh in judicial 

 balance the value of his contributions to human know- 

 ledge : considerations of this sort are overwhelmed in the 

 sense of irreparable loss to science. 



H. B. B. 



FERTILISATION OF FLOWERS BY INSECTS* 



IV. 



On the t'wo forms of/hnui:)- oj Viola tiicolor, aiitl on Iheir dijD'erent 



mode of fcrtilisalion. 



fTIOLA tricolor presents a further example of the same 

 ' kindofaimorphism as that described in the last article 

 in the case of Lysimahcia, Euphrasia, and Rhinanthus. 



* ConlinueJ from vol. viii. p. 435. 



One of its two forms, illustrated by Fig. 15 in natural size, is 

 more conspicuous than the other (Fig. 16), not only by its 

 larger size, but also by the more striking colour of its 

 petals. When the flower has just opened, its two upper 

 petals are light violet, or, in rarer cases, nearly white ; 

 but they gradually becoine a deep violet, or even dark 

 blue. Far more striking is, ordinarily, the change 

 of colour in the two lateral petals and the lower one, 

 which, immediately after the opening of the flower, are 

 nearly white, while in a fully-developed state they 

 are always violet. The petals of the small-flowered 

 form of Viola tricolor, illustrated in natural size by Fig. 

 i5, arc, on the contrary, uniform in colour and nearly white 

 during the whole time of flowering. The attractiveness 

 for insects of the two kinds must therefore be very dif- 

 ferent, whereas those particular marks round the opening 

 of the flower which serve as a guide to insects in search of 

 the honey, the " Saftmal" of Sprengel, are nearly the same 

 in the two varieties. That part of the lower petal imme- 

 diately before the entrance of the flower (y. Fig. 2 1, 22) 

 is in both dark yellow, and the lower petal is also 

 marked by black streaks converging towards the same 

 entrance. There is only this difference between the two 

 forms as to their guide-mark (Saftmal), that in the large- 

 flowered form seven black streaks on the lower petal, and 

 three on each of the lateral ones point towards the entrance 

 of the flower; whereas in the small-flowered form there 

 are but five black streaks in the lower petal, and none at 

 all on the lateral ones.* 



Although these two forms have been generally known, 

 at least since the time of Linnaeus, all botanists who have 

 published observations on the fertilisation of Viola tri- 

 color have apparently turned their attention exclusively to 

 the large-flowered form (Fig. 15), whose beautiful adapta- 

 tions to cross-fertilisation by insects, have been, therefore, 

 very accurately described ; while the peculiarities in 

 structure and fertilisation of the small-flowered form have 

 not even been mentioned. If, in this case, we clearly 

 see that even scientific inquirers have been far more at- 

 tracted by the larger violet flowers than by the smaller 

 whitish ones, wc need not wonder that insects are influ- 

 enced in like manner, and that from this cause smaller 

 and less conspicuous flowers are so frequently quite over- 

 looked by insects, that they would rapidly become extinct, 

 unless slight modifications of structure and development 

 enabled them to produce seeds by self-fertihsation. 



Indeed, in Viola tricolor, as in those species hitherto 

 considered, regular self-fertilisation in the small-flowered 

 form is effected by such slight modifications of structure 

 and development, that by far the larger number of the 

 contrivances in the large and small-flowered forms are 

 identical. 



In both forms, honey is secreted by two long appen- 

 dages («) of the lower filaments (yf), from which it ascends 

 by adhesion into the uppermost part of the hollow spur 

 (jr/j ; the style (,v/)'. Fig. 22) is directed downwards on its 

 base, slender and bent like a knee, while above it is straight 

 and gradually thickened, but does not increase at all or 

 only slightly in breadth, ending in a skuU-hke stigmatic 

 knob (/'), thick enough to completely stop the entrance of 

 the flower. This knob is provided with a wide open moist 

 stigmatic cavity (si,) and is protected from above by two 

 sets of hairs {/ir, Figs. 21, 22, Sprengel's " Saftdecke ") on 

 the two lateral petals, which at the same time defend the 

 entrance of the flower against rain, and prevent insects 

 from entering into the flower in any other way than by 

 the lower side of the skull-like knob. In both forms the 

 five anthers open inwards, are narrowed towards their 



* My description rebtcs exclusively to those v.irieties of yit^ta tricolor 

 which grow in the environs of Lippstadt. From Sprengel's, Bennett's, and 

 other descriptions and illustrations, lam aware that in other localities some- 

 what different varieties are lound. But I do not doubt that differences in 

 the manner of fertilisation, identical or closely allied with those hereto be 

 described, will be lound wherever a large-flowered and a small-flowered form 

 of l^ioiet tricolor co-<iy.\i.i. 



