60 SUMMARY OF CURRENT RESEARCHES RELATING TO 
live correlation, yet the symmetry of the two fins is not rigid. The 
pectoral fins are in negative correlation to the dorsal fins, in positive 
to the anal fins, hut the correlation could not always be demonstrated. 
Problem of Utility.*' — Captain F. W. Hutton replies to Mr. A. R. 
Wallace’s conclusion that, “ whether we can discover their use or no, 
there is an overwhelming probability in favour of the statement that 
every truly specific character is or has been useful ; or, if not useful, is 
strictly correlated with such a character.” He takes two tests of utility 
— adaptation and recognition-marks. Recognition-marks must be re- 
stricted to animals with eyes. What then of the colours of the shells of 
blind Lamellibranchs, the obscured venation of the wings in Lepidoptera 
and Trichoptera, the crabs covered with sea-weeds ? Their marks can- 
not be recognition-marks ; are they adaptations ? Adaptations are of two 
hinds : those useful to their possessors, and those which have been useful 
to former ancestors. We can eliminate the last group by restricting our 
attention to the specific characters of a species the habits of which agree 
with those of other species of the genus; for in these cases the habits 
must have remained the same during the whole of its specific life, and 
the specific characters must have been developed by their present pos- 
sessors. What, then, of the colours of the arenicolous species of Tellina , 
a spine more or less on a crab’s carapace, the branching of a wing-vein 
once or twice, the number and shape of teeth in snails, the ribbing of 
the shells, the shapes of the spicules in Holothurians and Sponges, the 
skeletons of Radiolarians, the ornamentation of Diatoms, and so on ? As 
a particular case, Hutton selects the species of Ptilopus (fruit-pigeon), 
thirteen of which arc found isolated on islands or small groups of 
islands. The colours are not recognition-marks ; they are not due to 
correlation ; they cannot have been useful to ancestors, since they have 
only lately developed ; and there is no evidence of adaptation to locality, 
since all the islands have practically the same climate, fauna, and flora. 
The author concludes that we are forced to look for an origin apart from 
utility for many a specific character. “ Just as gravitation does not 
express the whole of the relations between inorganic bodies, so, probably, 
selection does not express the whole of the relations between organic 
bodies.” 
Variations in the Brachial and Lumbo-Sacral Plexi of Necturus 
niaculosus.t — Mr. F. C. Waite has studied thirty specimens of this large 
perennibranch salamander, which were, in the main, procured from one 
locality in Lake Erie. The brachial plexus showed a tendency towards 
variation in the location of “ strength-centre ” (central with regard to 
the combined strengths of the component nerves) ; but this is not 
correlated with the variations in the position of the pelvic girdle, or with 
displacements of the strength-centre in the lumbo-sacral plexus. The 
variations in the lumbo-sacral plexus are grouped under three heads : — 
those in which the girdle is attached to the nineteenth vertebra ; those 
with the girdle carried by the twentieth vertebra ; and those in which the 
constituents of the girdle have an asymmetrical position. 
Two theoretical questions are asked : — (1) Does the abnormal posi- 
* Journ. Linn. Soc. (Zool.), xxvi. 1897, pp. 330-4. 
t Bull. Mus. Comp. Zool. Harvard, xxxi. (1897) pp. 71-92 (2 pis.). 
