Ccelentvrata from the North Atlantic. 421 



the more delicate Hydrozoa lacked organs which must 

 necessarily be examined before an unhesitating opinion 

 with regard to their position in a classification can be 

 formed. Their incompleteness was partly due to damage, 

 almost inevitable when such flimsy creatures are removed 

 from the depths of the Atlantic to an Oxford laboratory, 

 and partly to their having been taken in November, at a 

 season when senile decay has robbed them of organs charac- 

 teristic of the prime of life earlier in the year. 



Nevertheless, Mr. INIurray's collection of the Hydrozoan 

 fauna of the intermediate depths of the North Atlantic is 

 quite sufficient to indicate some important and interesting 

 facts of distribution. 



The material was collected on the 19th, 20th, 21st, and 

 22nd of Novem-ber, 1898, in various depths from 1 770 fathoms 

 to the surface, at about lat. 52° 20' N., long. 11° W. to 15° W., 

 about 200 miles west of Valencia. The method of fishing 

 has already been described by Mr. Murray in the ' Geogra- 

 phical Journal.-' Open tow-nets were towed in series at 

 ascertained depths, and it was intended that the organisms 

 common to the surface-nets and the deep nets should be 

 subtracted from the total catch of the latter, so as to discount 

 those organisms captured during the descent and ascent of 

 the nets. 



The method would be an absolutely perfect one if it were 

 possible to rely upon the plankton of the various depth-zones 

 being uniformly distributed during the interval of time which 

 must necessarily elapse between the lowering and the raising 

 of the series of nets. The obvious defect in the method is 

 that it might lead to erroneous conclusions if the plankton 

 be not uniformly distributed in a zone. The occurrence of 

 particular species in dense swarms is a very well-known 

 phenomenon, and it is not at all impossible but that open 

 nets during their descent to the deeper waters might catch 

 a great number of individuals of such a swarm which 

 might be altogether missed by the nets following employed 

 nearer the surface. However, although Mr. Murray's 

 method is open to this objection, I think that the final results 

 will show that it is a very useful and practicable one, and that 

 even if a certain proportion of the results be discounted 

 there will remain a balance in favour of Mr. Murray's 

 main contention that the deeper intermediate waters of the 

 ocean are inhabited by living organisms. 



The details of distribution are set forth in the accom- 

 panying table. The figures in the fifth column show the 

 number of individuals of all species captured in the nets 



