352 



NATURAL SCIENCE. Nov.. 



an immense number of very small specimens of Gonerichthi, the 

 young forms, as it is reasonably supposed, of the genus Gonodactylus. 

 Of larval Squillidae there is a most important discussion in Hansen's 

 work above mentioned. For the adult forms, the student will find 

 Dr. Bigelow's paper of very great service. 



Mr. Benedict's paper on the Lithodidae describes eleven new 

 species, and establishes four new genera. 



Several of the new forms seem to be interesting, and the descrip- 

 tions are no doubt adequate, but there are no illustrations. From a 

 naturalist's point of view, it is almost a calamity to have a new genus 

 instituted without any figures of the typical species. No skill has 

 ever made technical description agreeable reading, so that a new 

 form can only hope for welcome when, by the help of accurate 

 drawings, its distinguishing features can be perceived, if not at a 

 glance, at least without excessive tedium. 



Attention should be called to Dr. List's remarkable and amply- 

 illustrated essay on the locomotor apparatus of the crayfish. The 

 ordinary observer will, perhaps, be surprised to find himself confronted 

 in its pages with geometrical diagrams and the formulae of algebra and 

 trigonometry ; but there is much also which the unmathematical 

 reader can follow. For example, the author points out that the last 

 pair of walking feet in the crayfish push, while the three preceding 

 pairs pull, and that the position of the last pair facing the others 

 might lead us to expect a difference in its way of working. But so 

 little, he adds, has this characteristic been taken notice of in the 

 figuring of crayfishes that, even in Huxley's classic monograph, the 

 frontispiece represents the animal in a position which, if it ever occurs 

 at all, is, at any rate, a very constrained one. 



Since the above was written, Dr. List has published a valuable 

 Second Part dealing with the motor organs in a considerable number 

 of Macrura and Brachyura. To those who will follow his observa- 

 tions on the living animal, even a common prawn may become an 

 uncommonly interesting object. The circumstance that such an 

 animal has its body-segments (or somites) and its limbs and limb- 

 segments varying in length and strength, in shape and ornament, in 

 mobility and mode of attachment, may easily pass unadmired. But 

 when the nice adaptation of these characteristics to the creature's 

 economy is observed in activity, when, for example, the delicate fore 

 feet can be seen actually taking a mote out of Leand^v's eye, only a 

 churlish insensibility could refuse to be gratified. A human traveller 

 might be tempted to feel disgust at the cumbersome luggage and 

 unportable furniture of his own civilised state, when he finds how 

 compactly and readily a shrimp carries about its person the practical 

 equivalent of brushes and combs, knives and forks, sieves, thread, 

 cement, tongs and shovels, boat-hooks, paddles, and rudder. Dr. 

 List very properly alludes to the admirable observations already 

 made by Dr. C. W. S. Aurivillius on the relations between the 

 seemingly trivial details of structure and the really important 

 necessities of life in various Crustacea. The subject is a wide one, 

 with many interesting opportunities still unexhausted. 



In regard to the commonly accepted view that the trunk-limbs of 

 the decapods " consist in the Natantia of seven free joints," Dr. List 

 considers that it no longer has full validity, his investigations having 

 proved that in a series of forms " one joint may be subdivided into a 

 series of ' free ' jointlets, which are completely comparable to the 

 other joints." But it may be urged that, in deciding the normal 

 number of segments in the maiacostracan limb, one has rather to 



