SONNINIA PALMATA. 373 
tridactyloid, the inner bidactyloid—deeply divided by the outer interlobular 
cell ;' the outer lobule (A) of the superior lateral lobe greatly exaggerated and 
tripartite; the terminal lobule (£) very intra-axial, very anisosceloid, and very 
inequicellate ; the inner lobule (C) greatly abbreviated, very anisosceloid, partly 
coalesced with the terminal lobule, and feebly bipartite. 
The most noticeable feature in this species is the large superior lateral 
lobe. Of its unduly exaggerated outer lobule (A), the portion marked a’ 
(Pl. XC, fig. 9) is the homologue of the principal point of the outer lobule in 
other species; but in the present case, instead of being continuously projected 
from the side of the lobe, it is exceptionally dependent, whereby it almost apes 
the terminal lobule (B). The outer lobule has not only increased by extending a 
side-shoot, a’, but it has developed a further accessory shoot, a*; and it would 
be difficult to say whether a’ or a’ be the homologue of the upper shoot in such 
a species as papilionacea (Pl. XC, fig. 3). As may be seen by the lettering, it is 
suggested that a’ in fig. 9 and fig. 3 are homologous. 
The homologue of the terminal lobule of other species is the lobule lettered B. 
That such is the case, and that this lobule is in a somewhat degenerate condition, 
may be learnt by comparison with the suture-lines of Sonn. gibbera and Sonn. sp. 
(Pl. LXX XVIII, figs. 1—4). These suture-lines show the terminal lobule partly 
joined with the inner lobule, and they indicate that further abbreviation of the 
inner lobule might easily allow the terminal lobule to, apparently, occupy the place 
of the inner lobule. Such has been the case in this species; but it is not so 
much the abbreviation of the inner lobule (C), though that lobule is certainly 
degenerate, as the excessive development of the outer lobule (A), which has 
thrown the terminal lobule out of its proper position. 
Compared with almost bilaterally-symmetrical, cruciform superior lateral 
iopes (Pl. LVI, fiz, 2; Pl. LXXXI, fig. 9; Pl. LXXXIX, fig. 8; Pl. XCUL 
fig. 7), the phylogenetic developmental changes necessary for the evolution of the 
superior lateral lobe of this species are shown to be very remarkable. Excessive 
growth of the outer lobule which has partly usurped the functions of the terminal 
lobule, but has provided for the performance of its own normal duties by 
throwing out the side shoots a’, a’—the consequent proportionate abbreviation of 
the terminal lobule, coupled with a lateral shifting inwards, this lateral shifting 
causing coalescence with the inner lobule, whose functions are partly usurped—the 
usurpation of the functions of the inner lobule causing abbreviation or partial 
abortion of that lobule,—these are the changes which such a comparison indicates. 
Such changes have given the lobe a bifid character in the main; and its two 
portions have been further subdivided into three and two respectively ; for the bipar- 
tition of CO is only rudimentary. Thus the lobe is pentadactyloid ; and sucha shape 
’ 
1 The cells parting the terminal and lateral lobules may be called the “ interlobular cells.’ 
