TRANSACTIONS OF THE SECTIONS. 105 
the gradual development of the visual organ, since it must have been perfected long 
before such creatures could have come into existence under the genetic theory. 
Between the conflicting evidence afforded by such facts, which the author desig- 
nated “ rigidity of type,” and the plasticity or variability of form shown to exist 
by Mr. Darwin, in both the animal and vegetable kingdoms, he thought there 
was but one safe theory, ¢. ¢. ‘‘ that animals and plants varied, and are modified by 
natural selection within certain limits.” 
The author endeavoured to show that variability was a character inherent in 
certain organisms capable, like other characters, of being increased or diminished by 
selection in a number of successive generations. The slight amount of variation 
known to exist in nature compared to that of domestic and cultivated forms, was 
noticed at length, together with the amount and nature of variation in polymorphic 
or protean genera. Mr. Lowne thought it highly probable that accidental 
characters neither of use or the contrary to the individual, became fixed by isolation, 
especially amongst insects, where a single male is often capable of impregnating a 
whole isolated colony of females. 
The nature of the variation in Eucalyptus was stated to be quite unlike that of 
most variable forms, the leaves and flowers, according to the author's observations, 
being very variable in each species in characters usually most constant in other 
groups, so as to produce the greatest confusion in herbariums and scientitic 
descriptions, although he admitted that further evidence was wanted upon the 
subject. 
cieincs of character under competition was next discussed and stated to be 
extremely exceptional ; the gradual extinction of thirty species of Elephant and 
their reduction to two was noted as an example quite at variance with the theory. 
Lastly, the author stated that he believed Mr. Darwin’s theory was a most im- 
portant one, and thoroughly proved within certain limits; that the establishment 
of the existence of such limits was his aim, not the contradiction of a single fact 
advanced by that great observer; and he concluded by saying although it will 
perhaps always be impossible to draw a line between the constancy of type and the 
variation or modification of species, yet that future observers might assign a limit 
oy sufficiently near for the right interpretation of the Cosmos of Organic 
ature, 
On the Proboscis of Ommatoplea. By W.C. M'Intosu, M.D., F.L.S. 
In this paper attention was drawn to the structural differences between the 
Ommatoplean and Borlasian proboscides ; and the views of MM. de Quatrefages, 
Max Schultze, Van Beneden, Claparéde, and Keferstein, in regard to the structure 
of the Stylet-Region in Ommatoplea, commented on, with the aid of drawings. 
On the Boring of certain Annelids. By W.C. M*Inrosu, M.D., F.L.S. 
This paper was brought forward with a view to show that the chemical or acid 
theory, advanced last year by Mr. Lankester, cannot be applied to the boring of 
Annelids, any more than it has been found to explain all the facts connected with 
the perforations of Echinoderms, Gephyrea, Mollusca, Bryozoa, and Sponges, and 
to maintain the statement of the author (which Mr. Lankester had doubted), viz. 
that Leucodore ciliatus bores in aluminous shale. 
Instead of the boring of the latter species being new, as asserted by Mr. Lan- 
kester, it, as well as the chemical theory in regard to annelidan borings, was shown 
to be very old. Moreover the perforations occur in sandstone, as well as in alu- 
minous shale, calcareous rock and shell. The author also described the borings of 
Dodecaceria concharum (a species very frequently associated with the former), Sabella 
saxicava, Sipunculus, &e. 
On the occurrence of Lastrea rigida in North Wales. 
By Grorex Maw, F.L.8., F.GLS. 
With the exception of a single specimen found in the neighbourhood of Bath, 
