258 TREUBIA VOL. II, 2—4. 
SWELLENGREBEL himself declares in an appendix to his article (5), entitled: 
“Note to the tables and the graph”: “The number of larvae captured in 
“each category of finding places, should not be taken as a standard of the 
“orevalence of larvae in that category, for in some of those categories, 
“especially the inland fish-ponds, the catching has been carried out longer 
“and more intensively than for instance in the salt-water fish-ponds on 
“the coast, so that it might seem that in the former there occur more 
“larvae and especially more /zdlowi-larvae than in the latter, whereas in 
“reality it is just the other way about. Furthermore one might, for 
“the same reason, think that large lakes (Lake Manindjau) are unim- 
“portant for the /zdlowi-production ; but there are there, relatively, far more 
“Judlowi than in the fish-ponds; however only one catch was made there, 
“against daily catches continued for months in the fish-ponds”. In view 
of this statement I am surprised that SWELLENGREBEL (58) should have 
published his Table Illa, “stating the percentage of the total number of 
“larvae of each species captured in each category of breeding-places”, and 
the accompanying Graph representing the “distribution in percentages of 
the larvae of each species captured, over the eleven categories of finding 
places”. The table and graph referred to show nothing concerning 
the relative productivity of the different categories of breeding-places — 
in larvae of different species of Anophelines, indeed they may convey an 
erroneous impression thereanent. For a reader who does not go through 
the article carefully and critically from A to Z but who in the first place 
looks at the tables and such things, as may be expected to happen frequently, 
will in most cases, it seems to me, at least begin by thinking that the. 
intention of Table Illa and the accompanying Graph must be to give a 
survey of this relative productivity. Whilst SWELLENGREBEL himself 
says (°°) (page 58) that relatively the large lakes (Lake Manindjau) produce 
far more /udlowi than the fresh-water fish-ponds, his Table Illa gives for 
“ludlowi, interior’: 98°/, for the category of breeding-places “fresh-water 
fish-ponds” and 1,8°/, for the category “large lakes”! 
In the same way it seems to me highly improbable that the values 
given for “/zdlowi-coast” in Table Illa and in the corresponding Graph of 
SWELLENGREBEL for the categories of breeding-places “salt-water fish-ponds”, 
“salt water outside the fish-ponds” and “fresh water near coast”, which are 
in the same order 66°/,, 21°/, and 12°/,, should even approximately tally 
with the figures rendering the real relative productivity in Zudlowi of 
the said breeding-places. Now I know very well that SWELLENGREBEL 
does not claim that his table and graph should express that relative 
productivity, but it is hard to see what purpose is served by the publi- 
cation of his table and graph, unless they did express this relative 
productivity. 
In the case of the investigation by Mr. VAN BREEMEN and myself the 
catches with mosquito-nets yielded fully reliable and thoroughly comparable 
