Deckmbeb 14, 1900. ] 



SCIENCE. 



927 



BIOLOGICAL SOCIETY OP WASHINGTON. 



The 328th meeting was held on Saturday 

 evening, November 17tb, and was devoted to a 

 popular symposium on the subject of ' Malaria 

 from a Biological Standpoint. ' 



C. W. Stiles described ' The Structure and 

 Life History of the Parasites of Malaria,' illus- 

 trating his remarks with numerous diagrams. 

 He noted the various theories regarding malaria 

 and pointed out the steps by which our pres- 

 ent knowledge of its cause had been reached, 

 stating that Dr. A. F. A. King was the first to 

 suggest that the mosquito was the direct agent 

 in transmitting the disease. The manner in 

 which the parasite passed from the water to 

 the mosquito and thence to man was described 

 in some detail, and the fact brought forward 

 that various animals are subject to malaria pro- 

 duced by different parasites than those which 

 cause the malaria of man. 



L. O. Howard discussed ' The Malarial Mos- 

 quitoes, their Biology, what has been done 

 and what may be done to Exterminate Them,' 

 giving a full description of the biology of Ano- 

 pheles, contrasting it with the life history of 

 Culex and with the recently discovered and as 

 yet unpublished life history of Psorophora, il- 

 lustrating his remarks with lantern slides. He 

 dwelt at some length on the subject of mos- 

 quito control, describing the different remedies 

 and mentioning some cases in which, during 

 the past summer, not only had the mosquito 

 supply been greatly diminished, but in one ma- 

 larial village malaria had practically been eradi- 

 cated. He also described at some length the 

 results of a very interesting experiment in com- 

 munity work atWinchester,Va., where the treat- 

 ment of mosquito breeding places was made, 

 during the past summer, a police measure. 

 F. A. Lucas, 



Secretary. 



ZOOLOGICAL JOUBNAL CLUB OP, THE UNIVER- 

 SITY OP MICHIGAN. 



At the meeting of November 15th, Mr. Ray- 

 mond Pearl gave an account of work carried 

 on at Woods Holl on the reactions of the em- 

 bryos and larvse of Limulus. The normal 

 movements and reactions of the adult had 

 been studied, and a brief prefatory account of 



these was given. With this as a basis, the 

 question was investigated whether there occurs 

 a development of reactions comparable with the 

 structural development. The results showed a 

 distinct parallelism in many respects between 

 the morphological development on the one hand 

 and the psycho-physiological development on 

 the other. 



The Walking Movements. — Some time be- 

 fore the animal leaves the egg shell (or more 

 properly, the ' vicarious chorion ') purposeless 

 kicking movements of the legs appear. After 

 hatching, these movements continue, but grad- 

 ually become coordinated by practice, until the 

 perfected walking movement is produced from 

 them. 



The Swimming Reflex. — The swimming 

 movements of the larva in the tribolite stage 

 and for a week following the moult which termi- 

 nates that stage are diiferent from those of the 

 adult. The adult swims by a combined, coordi- 

 nated movement of the thoracic and abdominal 

 appendages. In the young larvse swimming 

 takes place by the action of the gills, the legs 

 being held perfectly quiet, strongly extended 

 over the anterior edge of the thorax. The 

 gills of the larva beat rhythmically from the 

 first in a perfectly coordinated way. This 

 movement begins within an hour after the ani- 

 mal leaves the ' vicarious chorion ' ; it is clearly 

 a reaction due to the stimulation produced by 

 direct contact of sea water with the gills. 



Normal respiratory movements begin some 

 time before hatching. The complicated chew- 

 ing reflex of the adult is absent in young larvse. 

 The burrowing habit arises as a modification 

 of the thigmotactic response of the larva. 



To mechanical stimulation there is but one 

 response, and this is the same, whatever part 

 of the body is stimulated. 



The phototactic, geotactic, hydrotactic and 

 general thigmotactic reactions were discussed. 



All the reactions were found to be of a pecu- 

 liarly definite machine-like character, as if 

 each were the result of the starting into 

 activity of a distinct mechanism by a stimulus. 

 The reactions appear as soon as their mechan- 

 isms are developed. So long as the mechanism 

 is intact the response always takes place in the 

 same way. The reactions can be analyzed into 



