No. 515] NOTES AND LITERATURE 



cm 



heads contain interesting matter that belongs here. This is 

 especially true of Conklin's paper on Linerges. It is practically 

 out of the question to give within the limits of a brief review an 

 adequate summary of the contents of this group of papers. The 

 Atlantic Palolo has been under observation by Dr. Mayer for 

 nine years, and various interesting details in the "swarming" 

 of this species have been made out. Besides the principal swarm 

 (near the last quarter of the moon, between June 29 and July 

 28) there may be a few smaller swarms before and after this. 

 Experiments indicate that moonlight falling on the rocks in 

 which the worms live is indispensable to the swarming. 



Mayer's studies on the pulsation of the medusa of Cassiopea 

 xamachana is a continuation of work of his previously reported 

 one. The idea that sea water is a balanced solution for this 

 species, and that the animal manufactures its own stimulant 

 to the rhythmical contractions by the "constant formation of 

 sodium oxalate in the terminal entodermal cells of the marginal 

 sense-organs," is still further dwelt upon. Mayer concludes, in 

 agreement with some other observers working on other animals, 

 that in this species, "conductivity of the subumbrella tissue is 

 independent of contractility. Dr. Cowles's article on the 

 "sand-crab" is especially distinguished at first sight by some 

 of the admirable illustrations it contains. It is shown that 

 this crab, in which one chela is decidedly larger than the 

 other, almost always digs its burrow with the side having the 

 smaller chela and enters the burrow after it is dug, with that 

 side in the lead. This, Dr. Cowles remarks, is probably ad- 

 vantageous to the animal in that the larger chela is in the 

 more favorable position for defense. It would seem that this 

 case might have an interesting bearing on the question whether 

 structures take their characteristic forms to meet demands 

 imposed upon them or are used to the best advantage for 

 the organism after they are in existence. In which service are 

 the chela exercised more, in digging or defending and cap- 

 turing? Possibly the question might be answered observa- 

 tionally. The investigator concludes that the crabs do not dis- 

 tinguish colors visually and do not hear in the ordinary sense ; 

 that they see outlines ; that the so-called auditory organs are equi- 

 liberating organs; that the tactile sense is well developed; and 

 that the animals have memory and profit by experience, and 

 form habits. 



The peculiar structure and habits of the walking-stick, 



