diameter of 20 cino over vfhich v.'ide nesh s:l.lk gauze was tiglrbly 

 stretchedo This I perriitted to sinlc to the bottom of the tarilc 

 after v/hich I v;ould roise it at a fnir rate of speedo The lorvne 

 contained in the coiumn of v;ater of T/hich the little silken ncft 

 vras the br.se iTould then settle on the net and could be counted 

 v.lth -lut trouble* Fi' on this fij^ure it v/as possible by simple 

 computation to approximate the nuraber if larvae in the tanko The 

 method is not very exact, the filtration coefficient has not teen 

 taken into account and the lai-vae are not equally distributed in 

 the rratere This hor-ever r/as to some extent compensated for by 

 repeating the count over various locations trithin the tanks For 

 comparing the daiiy nujabers of larvae present this method was 

 entirely useful* 



Attempts were made to ivork vdt'iout interruption but in this 

 we did not alv/ays succeed and usually it vrns the motors v/hich 

 caused the delo.yj The Evinj^ude, used as an auxiliary in 1919 had 

 to be ujilizod repeatedly but finally was not equal to the strain. 

 In 1920 a stationary mr.rine m^otor was used in reserve but this also 

 v;as unsuitablec Ao a retjult the stirring device vms frequently 

 stopped sometimes even for 24 hovirs at a time and these stoppages 

 vrore invariably the cause of great losses o 



The care of the motors, feeding of larvae, keeping the raft 

 clean, etc,, took two men •.■;ho relieved eacli other every half day. 

 Mien the- base of operations 'aas located at Zandkreek in 1919 

 quarters for the personnel were established in a houseboat anchored 

 near the rafto In 3ergen-op-Zoon it \7ris possible to live ashore 

 at Q considercbls saving in cost of i;.aintenance9 



, For the purpose of planting the young lobsters in the Coster 

 Scheldt repeated use was made of the "Albo.tros", a boat put at our 

 disposal by the Chairman of the Direction of Fisheries for the 

 y.'aters of Zeelando 



Chapter IV . 



Rearing the larvae© The results 



Experiments in 1919 were comiienced on June 4» In 1920 they 

 could be started on June 9» It was on the 4th of June in 1919 

 that f or +he first tine considerable nuinbers of larvae vrere obtained, 

 namely ISO specinents , and alreadj"- on the 20th of June the first 

 larvae in the fourth stage of dtovelopnent were observed© Sixteen 

 ■ days then vrore req^iired for the development fron the Int to the 

 4th stage* This result was encouraging, especially since the 

 motors often failed and once were out of comission for 48 hourso 

 The nenn temperature during this time was 17.7^ C« (in the after- 

 noon), often a temperature of 18'^ to 19° occurred, on but t}n-ee 

 days falling to 15°« The first stage had lasted five to six days; 

 the second, four to five; and the 3d, five days. That the first 



134 



