( 112 ) 



important deepsea-material, a greater number of shallow-water forms: 



a richer collection altogether, as many species of Cirripeds belong to 

 the coastal fauna. 



However, this table was not compiled especially to show the greater 

 number of species collected by the Dutch expedition. Its main object 

 is to point out that the deepsea-material of all the oceans and seas of 

 the world together, as far as Cirripeds are concerned, has after all no 

 other composition than that which was collected in a relatively small area, 

 the Malay Archipelago. For both collections that composition comes to 

 this, that after all only two genera Scalpellum and Verruca, in deeper 

 water, are represented by numerous species and that the other genera 

 which do occur in that deeper water are represented there by very 

 few forms only. It is true that the genera Scalpellum and Verruca, 

 in shallow water, are also represented by several species: we now 

 know 125 species of Scalpellum, which are so-called "good" species 

 and which in any case, almost without exception, can easily be 

 distinguished from one another; of these 90 live at depths of over 

 500 m. to ca. 5000 m. and 35 in shallower water. The number of 

 known species of Verruca now amounts to 36 ; of these 5 were 

 observed in shallow water and 31 at depths from 500 to ca. 3400 m. 

 In deep water, however, only these two genera found circumstances 

 specially favourable for the formation of new species, whereas the same 

 for other genera holds good in more shallow water. As an instance of 

 the latter the genus Balanus may be pointed out: of this genus by 

 this time over 60 species are known and, therefore, it can safely be 

 considered as one rich in species. However, only 5 of these have 

 been observed in water of a depth of 200 — 500 m. and of the latter 

 only 2 at a depth down to 564 m. On the other hand 55 species 

 of this genus are known, which inhabit the coast or relatively shallow 

 water only. 



The author thinks that at the present moment our knowledge is 

 by far too incomplete to permit of an explanation of phenomena of 

 this kind ; in such cases all we can do is to try to state and to 

 control the facts as accurately as possible and we must then confine 

 ourselves to considering it as a peculiarity of a few genera that their 

 numerous species divide themselves over so strongly divergent depths, 

 whereas it is characteristic of other genera that none, or a single, or 

 a few species only have been able to adapt themselves to somewhat 

 more considerable depths. 



It is remarkable at the same time, and this holds good for the 

 genus Scalpellum especially, but for most of the known species of 

 Verruca also, that such richness in species is accompanied by so great 



