A HISTORY OF LANCASHIRE 



pede. Somewhat later in the year these nauplii disappear and are succeeded 

 by the ' Cypris ' stage of the same barnacle. The adult creatures resulting 

 from this latter form then begin to settle down on all solid objects in the 

 shallow water and they become a great nuisance to fishermen by encrusting 

 the bottoms of their boats. Other crustacean larva? are the nauplii of cope- 

 pods, and the zoea stages of the crabs Carcinus, Portunus, and Cancer. 



About the end of March and the beginning of April diatoms appear in 

 great abundance, the principal genera being Coscinodiscus, Biddulphia, Chceto- 

 ceros, and Rhizosolenia. After lasting for a month or so the diatoms become 

 very scarce and towards midsummer may almost disappear from the tow-net 

 gatherings. About this time of the year the gelatinous alga Halospbeera 

 viridis becomes very abundant. This form is always accompanied by a great 

 mass of mucus which almost at once clogs up the meshes of the tow-nets 

 and prevents the latter from 'fishing.' Another common constituent of the 

 summer plankton is the flagellate Noctiluca miliaris, a common 1 cause of the 

 phosphorescence of the water at this time and later in the year. Noctiluca is 

 curiously restricted in its distribution. It appears in abundance all along the 

 north Welsh, Cheshire, and Lancashire coasts in inshore waters, and it may 

 reach out as far as the Liverpool N.W. and the Morecambe Bay light-ships; 

 but it does not appear to get into Manx waters, nor is it common in the 

 Firth of Clyde. Other flagellates are Ceratium tripos and J urea, but these are 

 not abundant. The ctenophores Pleurobrachia and Beroe also appear in the 

 summer, the former being at times especially abundant. The Larvacean 

 tunicate Oikopleura occurs also in the summer and autumn. During the autumn 

 months diatoms may again become abundant. Medusoids, the zoea and 

 megalopa stages of crabs, and the larva? of the shrimp also occur. Copepods and 

 the ubiquitous Sagitta form the bulk of the plankton and last until the begin- 

 ning of the winter. Then the abundance of the plankton undergoes decrease 

 and copepods form its principal constituent. This general scarcity in mass 

 and lack of variety in forms lasts during the colder winter months. 



SUM MART OF LANCASHIRE AND IRISH SEA INVERTEBRATE ZOOLOGY 



PROTOZOA 



Two hundred and forty species of Foraminifera were recorded in the British Association List 

 of 1 896. Radiolaria and Infusoria are practically unworked, though both groups are abundantly 

 represented. Quite recently the study of the parasitic Sporozoa has received much attention, and 

 the following forms are recorded : Glugea (Nosemd) lophii, G. stephani, G. anomalum, Sphterospora 

 platessa, and the remarkable Lymphocystis johnstonei. 



PORIFERA (Spmges) 



The sponges are fairly well known. Fifty-nine species were recorded in the B.A. List of 

 1896, of which five were new to science when first described in Lancashire waters. 



CCELENTERATA (Jelly-fish, sea anemones, etc.) 



Ninety-two species of Hydroids, 43 Hydromedusae, 2 Siphonophores, 4 Ctenophores, 

 3 Alcyonaria, and 22 Actinians, are recorded in the B.A. List. The strictly Lancashire forms 

 constitute only a fraction of this list. All the Hydromedusae are, however, found in the inshore 



1 But by no means the exclusive cause. Occasionally when the water is phosphorescent the tow-nets 

 may yield no organisms which are to be regarded as light-producing ones. In such cases the cause is no doubt 

 some photogenous bacterium. 



94 



