and Laboratory Methods. 1219 



This quick closing of the wound is thought to be due, in the first instance, to the 

 elasticity of the healing tissue. It was found that small pieces of stem without 

 perisarc were capable of regeneration. In some cases pieces about 1 mm. in 

 diameter developed into complete polyps bearing tentacles. The last general 

 subject considered was the reparation of pieces of the stem split longitudinally. 

 The method of carrying out the experiments was to divide the aboral two-thirds 

 of the animal into two cross pieces, and then to split longitudinally the more 

 aboral of these two. The polyps produced by each of the split pieces are sym- 

 metrical. The number of the tentacles formed by each of the three pieces was 

 determined, and it was found that the sum of the tentacles produced on the split 

 pieces was always greater than the number produced by the intact, oral pieces of 

 the same animal. The reason for this appears to be found in the relations of 

 the surfaces of the pieces. The sum of the volumes of the split pieces is evi- 

 dently equal to the volume of the unsplit piece, but the sum of their surfaces 

 stand to the surface of the uncut piece in the relation of \^, as they are approx- 

 imately cylindrical and of equal length. On the other hand, the relation of the 

 number of tentacles in split and unsplit pieces is -^-Jw. Reducing these two frac- 

 tions to a common denominator, we have ^-|^ and i|^f . The close similarity of 

 these fractions indicates the validity of the conclusion that the number of tenta- 

 cles formed is directly related to the extent of surface of the formative basis. 

 The paper is one of great interest and importance. R. p. 



Holmes, S. J. Observations on the Habits and This paper describes quite fully the 

 Natural History of Amphithoe longimana behavior and general " natural history " 

 Smith. Biol. Bull. 2: 165-193,1901. ° ■' , 



of the amphipod crustacean, Amphi- 

 thoe. The scope of the work is well indicated by the titles of the sections, 

 which are as follows : " Specitic Description, Habitat, Enemies, Food, Move- 

 ments, Nests and Nest-Building, Moulting, The Seat of Smell, Color and Color 

 Changes, Sexual Habits, The Disposal of Excrement, Timidity and Pugnacity. 

 Phototaxis, Thigmotaxis, The Instincts of the Young, Regeneration, The Effect 

 of Cutting the Animal in Two." Some points of particular interest are: 1. 

 Amount of food eaten. It was found that the animals eat in twenty-four hours 

 an amount of food, as estimated from the excrement voided, equal to approxi- 

 mately one-tenth of their own bulk. 2. Method of keeping a straight course 

 while swimming. The constant state of partial flexion of the abdomen, together 

 with the beating of the pleopods, tends to make the animal move in a curved 

 path while swimming. This tendency is counteracted by the rotation of the 

 body on the long axis through 180°, at frequent intervals. The result of the 

 frequent repetition of this rotation on the long axis is a fairly straight path, 

 having for component parts arcs of circles. This method of keeping a straight 

 course resembles that shown by some of the Protozoa. 3. Nest-building. The 

 nests, which are tubular structures open at both ends and attached to water 

 plants, etc., are constructed from a secretion which is poured out from glands in 

 the first two pereopods. This secretion hardens as it comes out, and is fastened 

 at different points by the pereopods touching their ends to the object on which 

 the nest is being constructed. New nests are built in a very short time, " often 



