566 TACK sKor.siuinc. 



rnsps miitcd undtT ono spi'cics in tin- work m i|Ut'st inn, l lioUt;li tlicsi' Imins Imd liccii (list in^uislicd 

 1)V iiri'cciliiijj; writers as spcciiil species mi aicdiiiil nl' i^renter uv iiiiiKirdilVereiices. 



is this iissuiupl mil cil (J. II. I-"' 'W l.l':if's (•(uici t'.' l''ni' se\rr:il reasons i1 seems to iiie thai 

 this t|iiesti()ii must lie aiiswereii in the ne<:ati\e. ■ ' 



Its uncertaintv is sliown l>\ the very laet that it is baswl excliisivelyon a material collected 

 at a phuT SI) rieli in cJoseK-related s|)ecies as the liav of Biscay. An assiimjition ol such a nature 

 must, in niv <)|)inii>n. Iiaxc a more certain liasis than that presented hy (J. H. I*'i i\\ l.h:!!. 



It would, ol course, lie desiralilc In pio\c <i|- dispid\'e this assumptioi) diicclly li\- exjteri- 

 ments in aquaria. This was uiilort miatelv. howcxcr. impossilile lor me hecause o| the dil'li( iilt\- 

 of keeping those foi'nis in lull xiLHUii' lor a loiiy period ol' time m aipiaria. 



.\nother method ol setting to work at this prolilem would lie to iincstigate closeK' the 

 plankton material from di.stricts which have lew species ol the genus Ciinchoccm and where 

 tliese species are comparatively distantly related to each other. Skager W.xk is a district of this 

 kind. It is certain that there are only three species of this genus found here — at least regularly 

 and to any large extent; this is shown with all the certainty that could l)e desired hy the careful 

 investigations carried out hv the ,,Conseil permanent intei nat i<inal pmir Texploration de la mer". 

 These three species, C. elegans (!. O. Sai^s, ('. ohtumtd (\. ( ). S\l;s and (\ harralis (i. ( ). Saiis, 

 represent three tvpes of this genus that diffei' comparatively widely from each other. 1 have 

 had material from this region at my disp(«al. This material comprised (1) numerous mature 

 individuals and (2) larvae (of two or three different stages) of all these three species. On account 

 of the characteristic shape of the shell in these species the larval forms are very easy to distinguish 

 from each other with certainty. The fact that Ixitli larvae and mature individuals were found 

 of all these three species shows, of course, with complete certainty that wo are concerned with 

 throe different .species and that none of them can bo a ,, stage" of the other. It is certain that 

 the nmturo specimens all belonged to the same stage. The variations in size woie strikingly 

 small: C. ehgnm: <? = 2,05—2,25 mm.; ? = 2,0—2.15 mm.; ('. nhlusnta, ^ = 1.15—1,35 mm., 

 $=1.6—1,85 mm.; C. horealis, d> = 2,10— 2,20 mm.. ? = 2,5— 2,7 mm. Other characters 

 were practicallv (piite constant in these specimens. The same result was obtained by the 

 investigation of the material collected in February and that of August, a fact that is connected 

 with the phenomenon that the development of the Halo c y p r i d s (like that of the (' y p i' i- 

 d i n i d s) takes place continuously during the whole year. (Among the mature females that 

 were investigated there were both old and young specimens; some of them had very small, 

 others more or less large, eggs.) 



I arrived at the same result after investigating the FT a I o c y p rids from the Arctic 

 and the Antarctic Oceans. 



It seems to be impossible to retain G. H. Fowler's view under these circum.stances. 

 Nor does it seem to me necessary to criticize in detail the exposition put forward by this writer; 

 I refrain from doing so all the more as such a criticism would necessarily be very lengthy, without 

 the result being of any great value. Only a few striking facts need be pointed out. 



In spite of oljvious efforts G. H. FOVVLEH could not find two mature stages for more 

 than eight of the species investigated bv him; onlv one mature stage was found of the otliei' 



