Additional unfavorable factors in 1919 v/ere the inolenent 

 v/enther and the lov; tenporature in July, the nost important period 

 of the season*. GroYk-th was thereby greatly retarded as was noult- 

 ing and a spread of external parasites appeared rrhich would have 

 been best counteracted by a rapid succession of noultings whereby 

 they v/ould have been removed. 



Since, in cour climate, the frequency of cold surjiers must be 

 taken into account, that drawback also \7as in so far as possible, 

 met by moving}; the entire installation to an inland oyster bed at 

 Bergen-op-Zoom» The temperature of the water is influenced more 

 quickly here by the temperature of the air but althoui^h the heat 

 of the sun is sooner noticeable in the tejnperature of this water 

 it also cools off faster and becoriies colder than op.en water. In 

 general hov/ever the advantage v/as with this enclosed oyster bed« 



A great difficulty vras also encountered in .the keeping clean 

 of the T/ater in the tanlcs as well as the vj-alls and screens. The 

 latter, particularly those in the bottom became fouled and grevj- 

 shut to seme extent so that changing of the vroter Viras obstruct ed* 

 This was the reason v;hy in the new tanlcs bottoia- screens were 

 eliminated and that instead all fovir sides were supplied vriLth 

 relatively large windc.TS v/hich furthermore vrere removable for 

 cleaning without interfering with the functioning of the tanics. 

 Eventual weak places in the screens are then also easier to notice 

 before their breaking may lead to catastrophic corisequGnces. In 

 1919 it happened repeatedly that holes appeared in the screens or 

 that they became dislodged by the rusting out of iron nails v;hich, 

 in contact with the copper, eroded promptly. Af'ber th:'.t, copper 

 nails were useci, it is no wonder that v;ith all. these handicaps 

 the number of young lobsters resulting was not large. As has 

 already been stated, the greatest m.ortality now occurs when the 

 larvae' are v/ell along and begin to pass into the 4th stage. I 

 have not been able to find a single hint v;hich could lead to the 

 cause for this fact. During the ensuing season this will be the 

 mr.in issue upon which concentration vj'ill be focused. 



In 1919 much trouble vras experienced, from fungi and diatoms 

 living on the larvae. The last named vj-ere .easily and promptly 

 disposed of by shutting out the light from the tanlcs by covering 

 them virith canvas; as can be seen in fig. 8. At the time harever 

 it v/as ir^ossible to properly rid ourselves of the fungi. Yflriether 

 to rego.rd them as parasites or vriiether they used the larvae only 

 as a base to grow on I hove not been able to determine. In the 

 event the latter is the cose the only disadvantage of their 

 presence \Tould be the interference they imposed upon the moving 

 about of the larvae and the attendant handicap to their breathing 

 anr] feeding. If the hy-pha arc densely placed, food particles and 

 infusoria collect between the threads so that the larvae are 

 surrounded by an impiore layer deficient in oxygen. 



139 



