i82 Report S.A.A. Advancement of Science. 



figure of T. fiskii, P.Z.S., 1886, pi. LVIII.), and more especially 

 in ocidifera. The middle of the ocellus is constituted by the lateral 

 secondaries, and, if these are bifurcated, still more distinctive 

 " ocelli " are produced. 



When the simple ray type of coloration found in the tentoria 

 sub-group is compared with the complex ocellated pattern of some of 

 the ocidifera sub-group, the two would seem to be very divergent and 

 unrelated, and it is only by studying intermediate stages that the 

 pattern of ocidifera admits of comparison with that of tentoria. The 

 members of the -uerrcaiixii sub-group are particularly instructive for 

 this purpose. They include all stages in the prominence of the prim- 

 ary rays and their correspondence with those of adjacent shields 

 so as to strengthen the geometrical plan. Ocelli are also very clearly 

 indicated in some of the extreme members. The geometrica sub- 

 group also shows the same tendency towards the regularity and cor- 

 respondence of the rays, but to a much less degree than most 

 verreauxii ; indeed the colour pattern of some of its members cannot 

 be distinguished from that of tentoria. In trimeni the pattern seems to 

 have become more fixed and regular, and is transitional in character ; 

 rarely any of the tertiary rays are present, and usually *not all the 

 four secondaries. 



Taking all the representatives of the geometrica-gxoxx'p into 

 account, it becomes an easv matter to arrange a continuous series 

 showing all the transitional stages from the simple ray pattern of 

 tentoria to the very complex, ocellated display of ocidifera. No one 

 can question that all the colour variations are genetically related in 

 a direct line from such a form as tentoria to that of ocidifera, and 

 that they represent a strictly continuous type of transformation. Cor- 

 responding rays can be traced all through tlie series, the modifications 

 consisting in the closer relationship of those of one shield with those 

 of adjacent shields, and in minor changes such as bifurcations. In 

 certain of the sub-groups one transitional stage appears as if becoming 

 fixed, while in other sub-groups another stage predominates, but 

 probably nowhere do we get two individuals exactly alike. Even in 

 specimens of any sub-group from the same locality there are great 

 differences in the number of complete and incomplete rays present, 

 and in the regularity of the pattern. While conforming closely to the 

 general plan of the sub-group, the minor variations are innumerable. 



b. Coloration of Plastron. 



The plastron also affords a very complete gradational series in 

 the production of an elaborate colour pattern. The coloration of cer- 

 tain members of the tentoria sub-group may be regarded as the 

 extreme type of simplicitv, while that of ocidifera represents the 

 extreme of complexity. Between these two there is a complete varietal 

 series, showing that all are genetically related. 



In what may be considered as a typical tentoria, the whole of 

 the central part of the plastron is uniformly dark brown or nearly 



