U8 



PKOF. \\*. A. HERDMAN ON THE DISTRIBUTION 



Paracalanus. 



Paracalanus parvus (Clans) is a southern form (fig. 16) which extends to 

 the tropics and has a wide distribution. It is present in quantity only during 

 autumn and winter in the Irish Sea, being practically absent between 

 February and July, and having its maximum in September or October. The 

 largest hauls are in autumn, for example, 59,460 on September 7th ; 138,300 

 on September 10th; 53,500 on September 15th, nil in 1914; 61,930 on 

 August 24th, 1911; 49,800 on September 8th, 1910; 49,390 on September 

 7th, 1912 ; 44,060 on October 24th, 1912 ; while other large hauls in the 

 same months range from 25,000 to 40,000. 



Fib. 16. — Paracalanus parvus, from a photo-micrograph by A. Scott. 



This is a species that has varied considerably in quantity from year to 

 year, its average per haul ranging from 335 in 1907 to 5863 in 1914. In 

 the present year, 1917, it was especially abundant at Poit Erin in September, 

 along with Oithona. 



OlTHONA. 



Oithona lielyolandica (=0. similis), Glaus, is the most generally abundant 

 Oopepod throughout the year in the Irish Sea ; but the months when it is 

 taken in greatest numbers are June to November (inclusive) with the 

 maximum generally in Jul}-. There may, however, be a second maximum 

 later, in October or November. 



The following may be quoted as exceptionally large hauls : — The highest, 

 225,450, is on July 18th, 1911, and the next highest, 199,300, is on 

 November 9th, 1914 ; then we have 93,580 on July 28th, 1913, 87,530 on 

 September 26th, 1912, and 83,550 on June 14th, 1910. We have twenty 

 other records of over 44,000 each scattered over the months June to 

 November. This is the Copepod which has the highest average number per 



