286 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



more plankton hauls have been taken than was ever the 

 case before, and that these collections have been most 

 carefully and critically examined by experts. For 

 example, in the last three years nearly 2,000 gatherings 

 from the sea off Port Erin have been quantitatively 

 reported upon, while before that time 50 in the year was 

 probably a fair average number, and the examination of 

 the material was qualitative only. So it is only what 

 might be expected if the minuter and rarer and more 

 critical species are now being found to be present where 

 previously unrecorded; and we know that species which 

 are usually rare may, through some change in the 

 conditions, such as the competition with allied forms, 

 become temporarily or locally very abundant. We have 

 no proof that this is the explanation of the recent 

 manifestation of Biddulphia sinensis, and we only mention 

 it as being worthy of consideration before we accept as 

 established the view that this species is a new immigrant 

 from the Red Sea or more eastern waters. It must be 

 remembered, however, as telling against this alternative 

 explanation, that B. sinensis was not noticed during the 

 two first years of our more intensive collecting, and more 

 exhaustive examination of the material, and that a 

 re-examination now of that earlier material reveals no 

 trace of it. We are, therefore, inclined to consider that 

 when this Diatom was first noticed in our nets early in 

 November, '09, it had recently entered the Irish Sea for 

 the first time. 



Copepoda— Adults and Larvae. 



In the examination of the catches, the adult 

 Copepoda, the Nauplii and the young intermediate stages 

 (classed together as k ' juveniles ") have been counted and 

 recorded separately, and if we represent these records by 



