No. 378.] REVIEWS OF RECENT LITERATURE. 447 
This unknown force does not operate an infinite distance, but is 
limited to an area the radius of which is about three miles. 
In conclusion, then, the author finds nothing in the phenomena 
exhibited by bees or ants to prove the existence of any psychical 
quality. They learn nothing, but act mechanically in whatever they 
do, their complicated reflexes being set off by simple physiological 
stimuli. CASWELL GRAVE. 
Studies on Hair. — In the last number of the /enazsche Zeitschrift 
(vol. xxxi, p. 605) Dr. Fritz Romer continues his studies on the 
integument of mammals in an article dealing with the arrangement of 
the hair on the African rodent Zhryonomys swinderianus. In an 
embryo of this species, about sixteen centimeters long, the head, 
trunk, extremities, and base of the tail seemed covered with rows of 
small scales. On closer inspection this appearance was found to be 
due not to scales, but to the arrangement of the hair. The hairs were 
placed in short, slightly curved rows, each row containing three, five, 
eight or twelve hairs. While in any row the middle hairs were longer 
than the lateral ones, no single, large, central hair could be distin- 
guished, as de Meijere has found in the hair groups of so many 
mammals. Römer explains the rows of hairs in Thryonomys by 
assuming that they were originally developed on an ancestral form 
covered with scales, the rows of hairs alternating with the scales, and 
the scales afterwards disappearing. Since the publication of de 
Meijere’s paper on the hairs of mammals this theory has been 
gaining ground. Beside these regularly arranged hairs the embryo 
examined by Rémer showed many small, irregularly scattered hair 
germs which, upon further examination, were shown to give rise to 
the fine hairs of the thick winter fur, the summer fur consisting 
almost entirely of the regularly arranged hairs. The summer fur, 
then, presumably represents a hair arrangement phylogenetically 
older than the winter fur. po. Be. 
The Eyes of Amphioxus.— The organs of vision in Amphioxus 
have been made the subject of careful study by Dr. R. Hesse.’ They 
consist of very simple direction eyes, lying close to the central canal 
of the spinal cord. They occur from the third muscle segment very 
nearly to the tail. The eyes are not uniformly distributed along the 
cord, but are arranged in segmental groups, the groups corresponding 
to the muscle segments and, consequently, alternating on the two 
1 Tiibinger Zoologische Arbeiten, Bd. ii, No. 9, 1898. 
