1897. NOTES AND COMMENTS. 87 



is used as an insecticide to keep away the destructive white ant. Its 

 spiny leaves render it a very effective hedge-plant, and it has been 

 extensively introduced for this purpose in the Mediterranean region. 



A third paper is a short account of native ligulate Wolffias, 

 small fresh-water plants closely allied to our duck-weed, by C. H. 

 Thompson. 



The Occurrence of Marine Organisms. 



Many of the organisms commonly found in the plankton of the 

 sea around the British Coast exhibit remarkable variations in their 

 relative abundance at particular localities from year to year, but little 

 is known as to the extent and causes of such variations. As a number 

 of naturalists make use of the tow-net at many places round the 

 coast, especially during the summer, much valuable information 

 would be obtained, if in all cases records were kept of the presence 

 or absence of a limited number of the commoner species, and these 

 records subsequently brought together. 



The Director of the Marine Biological Association of the United 

 Kingdom has taken this subject in hand, and desires to tabulate the 

 results before January 31st, 1898. The following is a list of the forms 

 upon which information is desired, and it is followed by the nature of 

 the information asked for: — Halosphaera viridis; Noctiluca miliaris; 

 Aurelia aurita (including Ephyrae); Agalmopsis; Muggicea atlantica; 

 Hormiphora plumosa; Beroe; Tomopteris; Anomalocerapatersoni; Doliolum; 

 Salpa. Where the generic name only is given in this list, the specific 

 name of the specimens taken should be added. Should any doubt 

 exist, preserved specimens should be kept. In making a record the 

 following should be stated : — Date ; Hour ; Locality, (with as much 

 accuracy as possible) ; Depth, (depth of water, and maximum depth at 

 which net has been worked); Quantity, (o, absent ; i, few only; 

 2, moderately plentiful ; 3, exceptionally abundant). Observations 

 on the temperature of the sea, and notes on wind, tide, &c., will also 

 be of value. Records should be sent in before January 31st, 1898, or 

 forwarded from time to time to the Director, Marine Biological Asso- 

 ciation, Plymouth. 



The Problem of a Parasitic Copepod. 



Let the impatient reader purchase 500 specimens of the Norway 

 Lobster. Mr. J. Stewart Thompson {Proc. Phys. Soc. Edinburgh, vol. 

 xiii) offers him the hope of discovering upon these as many as four 

 specimens of a curious parasite. In the inevitable ' preliminary notice' 

 he introduces us to an unnamed, unfigured, dimorphic (but in the 

 female sex almost shapeless) animal, which he has found parasitic on 

 the vas deferens of Nephrops norwegicus. He believed it to be a 

 Copepod of the family Lernaeopodidae. In the members of that 

 group no peculiarity of situation, no oddity of form, can any longer 

 excite surprise. What really surprises is that the Demonstrator 



