1G8 MKKISTIC VARIATION. [PART I. 



mate to a ^i\.-n pattern. The highest number of ovaries, for 

 , recorded, is 7 pairs : hut there is nothing to shew that 

 aente mi^ln n.t undergo similar Homoeosia (The pro- 

 vi diminution in size of these ovaries from before back- 

 wards in this case i- \\orth noticing.) 



7. Tin- principle so often manifested in the evidence of 

 Variation, that the magnitude, completeness, and symmetry of 

 a variation l.-: t r- no necessary proportion to the frequency of 

 oreunvnee of that variation, is here strikingly exemplified. 



8. 'Id'- evidence as to the existence of two varieties of 

 r.ii-/,t/ilri!>i* .sy///'/<7//'Y/, //////, the one with all the organs a segment 

 higher than their place in the other variety may be well com- 

 paivd with SiiKititi.\(;TON's observation, that in the Frog and 

 in several Mamnial> (see Xo. 70) the individuals could be 

 roughly divided into two classes according as the lumbo-sacral 

 pi. -MIS was formed more anteriorly (" preaxial class") or more 

 posteriorly (' po-ta \ial class"). 



9. In the evidence as to Perionyx, it was seen that many 

 of the arrangements found occurred in single specimens only, 

 -i ingesting the inference that the systems do not fall into one 

 of these conditions more easily than into others; nevertheless 

 of each of three abnormal arrangements two examples were found, 

 a circumstance hardly to be expected on the hypothesis of for- 

 tuitous Variation. 



10. It is perhaps unnecessary to point out that the examples 

 of Variation given are in their several degrees Discontinuous, and 

 that by the nature of the case the Variation by which the several 

 -peeitic forms have attained their particular numbers and charac- 

 teristic disposition of organs, must almost of necessity have been 

 thus Discontinuous. 



CESTODA. 



The following facts ivspeeting Variation in Cestoda are chiefly 

 taken from LKI < KART, Piirnsitcn des Menschen 1 . 



the variations here enumerated, abnormalities of several 

 other kinds (\ari.-ition in number of suckers, prismatic segments, 

 Uit'uivatioii. AC.) are known in this i^roup, l>ut as these do not directly 

 illustrate the Variation of Linear Series, consideration of them must 



lie (Ict'elTeil. 



The degree to which the parts hearing sexual organs are 

 -p.-u-a ted from each other differs greatly in the various groups 

 of < 'erodes. In some (2We//opAonw) the segmentation amounts 

 to an inconsiderable const rid ion, while in /,i ; /,,l<i the generative 

 organs are repeated several times in a common body. L., p. 347. 



1 In what follows tin.- Irttrr L. is u<ccl in reference to this work. 



