52 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
to require a new family of Nudibranch Opisthobranchia. That it is an 
Opisthobranch is shown by the right-side position of the kidney opening 
and of the separate genital ducts, and by the hermaphrodite organ. 
That it is a Nudibranch is indicated by the strong concentration of the 
central nervous system with the ganglia mainly dorsal, and by the 
relatively long pedal commissure, as also by the complete absence of a 
shell. A remarkable feature is the finger-shaped foot. So is the 
presence of a large transparent cascum arising from the stomach, perhaps 
respiratory or hydrostatic in function. The body is laterally compressed, 
there are no eyes or tentacles, the radula is rudimentary or absent. 
Only one specimen was obtained. It has only convergent resemblances 
to Phyllirhoc. J. A. T. 
Victorian Chitons. — Edwin Ashby {Proc. Roy. Soc . Victoria , 1921, 
33, 149-58, 1 pi.). Description of Rhyssoplax jacksonensis sp. n., 
Lepidopleurus iredalei sp. n., and a number of other forms. J. A. T. 
Arthropoda. 
a. Insecta. 
Persistence of Traces of Wings in Worker Ants.— Harlow 
Shapley ( Proc . Nat. Acad. Sci., 1921, 6, 687-90). The embryonic 
vestiges of wings discovered by Dewitz in workers of Formica do not 
invariably disappear with the passing of larval and pupal stages, but 
occasionally persist to the adult state. Wheeler has called such winged 
workers “ pterergates,” and nine cases have been recorded as rarities. 
From a nest of the red Californian Harvester, however, Shapley has 
taken during two years more than 1700 workers, nearly one half of 
which showed vestigial wings in various stages of development. This 
suggested that Mendelian factors might be involved in the appearance 
of wings. There was no obvious external reason why the nest in question 
should show the peculiarity. In fifty colonies within a radius of two 
miles only one pterergate was found. In all details of thoracic structure 
the pterergates agree with normal ergates, and they participate equally 
in excavating and guarding the nest and in harvesting. The seventeen 
young queens and two males taken from the nest were quite normal. 
Of the 740 pterergates, 385 showed minute veinless wing-sacs or stubs 
of broken wings; 219 showed sacs from 0 # 5-l mm. in length with 
indistinct veining ; and 132 had transparent, clearly veined winglets 
from 0 • 8 to 1*5 mm. long. The gradation is perfectly continuous, 
which may be of interest in connexion with the origin of castes. Four 
ants from the affected nest had vestiges of both posterior and anterior 
wings. In all other cases only anterior wings were represented. 
J. A. T. 
Thermokinetics of an Ant. — Harlow Shapley {Proc. Nat. Acad . 
Sci., 1920, 6, 204-11). From the measurement of the speed of a 
thousand individuals of the ant Liometopum apiculatum , an empirical 
curve was obtained that for any temperature throughout a range of 
30° C. gives the speed with an average probable error of 5 p.c. for one 
observation. Conversely, from a single observation of the ant-speed,. 
