544 



SCIENCE 



[N. S. Vol. XLIX. No. 1275 



After discussing the mode of occurrence, 

 conditions of preservation, manner of life in- 

 cluding method of progression, food, defense 

 and offense, the author describes species with 

 appendages, which include besides the genera 

 already mentioned, Kooienia dawsoni (Wal- 

 cott), two species of Ptychoparia including a 

 new one P. permulta from the Burgess shale 

 quarry, Odonotopleura trentonensis (Hall), 

 Trinucleus concentricus Eaton, and an un- 

 identified Ordovician crustacean leg. The 

 work of C. E. Beecher with Triarthrus is 

 reviewed in some detail, and a different con- 

 clusion arrived at in certain features. 



In section two of the paper the structure 

 of the trilobite receives attention, the author 

 again referring to Beecher and other writers 

 including Jaekel, Beyrich, Barrande and de 

 Yolborth. He then discusses in detail the ap- 

 pendages, summarizing them as follows: 



Cephalic: (1) Antennules, (3) antennse, 

 (3) mandibles, (4) maxillula, (5) maxilla. 



Thoracic : 



Ahdominal: 



Caudal rami: 



Further comparisons are with the recent 

 Anaspides tasmaniw G. M. Thomson, a Mala- 

 costracan from Tasmania, Eoonunga cursor 

 Sayce, and Paranaspides lacustris Smith, also 

 the parasitic crustacean Cyamus scammoni 

 Dall, illustrations of all of which are given. 

 After the extraordinary interest of the finely 

 developed specimens in the plates representing 

 Neolenus, attention will be drawn by those of 

 Isotelus, Triarthrus hechi Green, and other 

 Ordovician trilobites, together with the sec- 

 tions of Cambrian and Ordovician trilobites, 

 and finally the author's conclusions as ex- 

 pressed by several diagrammatic restorations, 

 also sketches of thoracic limbs of trilobites 

 and recent crustaceans, crustacean limbs, and 

 six plates of tracks and trails of trilobites, 

 each adding evidence to the author's deduc- 

 tions as to the appendages. 



Some conclusions drawn are that the trilo- 

 bite's appendages show him to have been a 

 marine crustacean far more highly developed 

 than would have seemed possible in a period 

 60 infinitely remote. 



In its younger stages of growth a free moving 

 and swimming animal, it later became a half-bur- 

 rowing, crawling and sometimes swimming animal 

 and moving at times with the flow of the tides and 

 prevailing currents. Eggs have been found both 

 within and free from the body. ... It was at home 

 on many kinds of sea-bottom and was able to ac- 

 commodate itself to muddy as well as clear water. 



It was intensely gregarious in some localities and 

 widely scattered in others, depending upon local 

 conditions, and habits of the various species. 



Trilobites had an ample system of respiration by 

 setiferous exopodites, epipodites, and exites at- 

 tached to the cephalic, thoracic and abdominal 

 limbs [as shown in restorations of the limbs on 

 plates 34 and 35]. 



The structure of the gnathobases of the cephalic 

 limbs indicates soft food such as worms, minute 

 animal life and decomposed algae. . . . The trilo- 

 bite persisted from far back in pre-Cambrian time 

 to the close of Carboniferous time . . . and left 

 its remains more or less abundantly through about 

 75,000 feet of stratified rocks. 



The paper is profusely illustrated and care- 

 fully indexed. 



G. E. Brigham 



SPECIAL ARTICLES 



PRESOAKING AS A MEANS OF PREVENTING 

 SEED INJURY DUE TO DISINFECTANTS 

 AND OF INCREASING GERMI- 

 CIDAL EFFICIENCY 



In the course of investigations on the bac- 

 terial black^chaff disease of wheat, under the 

 direction of Dr. Erwin F. Smith, a new method 

 of seed treatment has been discovered which 

 practically eliminates seed injury due to the 

 use of disinfectants, and at the same time 

 renders pathogens on the seed coats more sus- 

 ceptible to the action of the disinfectant. 

 This is accomplished by allowing the seeds to 

 absorb water for a definite period in advance 

 of treatment. The saturation of the cells and 

 cell-walls with water before treatment, by di- 

 luting the full-strength disinfectant beyond the 

 point of injury as it enters the tissues, in ac- 

 cordance with the law of diffusion of dissolved 

 substances, is the explanation of the results 

 obtained. Not only is injury to germination 

 prevented, but the germination of seeds thus 

 treated is stimulated, reducing the danger of 



