to the effects of variations of aary external environmental feet or s 

 on the littoral animals. ..-.:•. ■ "" 



One of these studies is carried out on the lobster larvae just 



•after hatchirig*' .' ■ ■ 



One knov/s that the adult lobsters live on the bottom and thet 

 the females carry their eggs under the abdomen for nearly a year 

 -.before they hatch* They draw closer to the shore at the moment of 

 , spavming which happens especially in July and August, at the tine 

 of the inaximuia surface v;ater temperature o The hatching occui's in 

 the ev,ening (Fabre-Domergue and Bi^trix) and the young larvae dis- 

 perse./ 'making for the upper layers where they svj-ir; actively diiring 

 ali.io,st'a month, up to after the foui'th moult. Various authors 

 (Herriclc, Mead^ Hadley^ Plavinga) have noted that the speed of 

 development is greatly reduced v/hen the temperature is.lowi-erad: 

 for example s for the American lobster the first stage, v/hich may 

 last from one to five days at ¥oods Hole at 21 degrees, may be 

 prolonged up to 25 days at Rhode Island in a vmter temperat-ore of 

 15 sS degrees* 



V\re have sought the limits of temperature, salinity and pH 

 which are able to support the larvae of stages one and two caught 

 v/ith a fine net at the surface of a reservoir for lobsters* 



The enviroTiments for the various temperatures ere easily ob- 

 tained by means of the constant temperr.ture block of Cardot, 

 LaiAgier and Legendre (C, Ro de la Socc de Biolr, 1924, t. XCI, 

 •p» 331)9 Some larvae, happening to be caught, are introduced into 

 a series of ten tubes, each containing 20 o.c, of sea water, 

 placed in the block v;ith* constant temperatiares graduated from 22 

 to 4:0 degrees* 



The waters of various salinities are prepared by mixing sea 

 r, vmter of 1025 density either v/ith fresh water or with sea water 

 concentrated up to 1060 by evaporation. One pours 50 c*c» of each 

 ■ mixture, into a series of sina.ll crystallizing dishes where the 

 densities graduate regularly from 1000 to 1060, and one introduces 

 some larvae into each vessel* 



The different pPIs, from five to nine,, are realized by the 

 mixing of sea v/cter (pH 8«2) and the same (sea vrv.ter , that is) put 

 into equilibrium with a nil tension of CO^ (pH = 9) or v/ith the 

 same (sea vrater, that is) satiArated \7ith CO'' (pH = 5)," acb.ording 

 to the technique indicated by one of us (Legendre, La concentration 

 en- ions hydrogene de I'eau db mer* Paris, 1925, po 239)o 



116 



