42 JOURNAL OF MARINE ZOOLOGY AND MICROSCOPY. 



Plate IV, Fig. 1 — 8. Diagrams of the types of Canal System, 

 f. 1. Ascon ; f. 2. Chambered Ascon ; f. 3 & f. 4. Sycon ; 

 f. 5. simplest possible Rhagon ; f. 6. Eurypylous Rhagon ; 

 f. 7. Leucon or Aphodal Rhagon ; f. 8. Diplodal Rhagon. 

 All these are shown in vertical section, saving Fig. 4 

 which shows transverse section. In the Rhagon diagrams, 

 the white portion represents the greatly developed meso- 

 derm. The shaded portion denotes where ciliated cells 

 occur. Arrows denote the direction of the water currents. 



Study V. — A contribution to our knowledge of the 



COPEPOD MONSTRILLA ANGLICA. 



This species is for many reasons extremely interesting. A single 

 specimen, a male, was captured in 1857 by Sir John Lubbock (1) at 

 Weymouth, and at the publication of the concluding volume of 

 Prof. Brady's fine monograph on the British Copepoda (2) in 1880, 

 no further record had been made and the original specimen had been 

 lost. Just about this time the record was resumed by the capture off 

 Jersey, of a few specimens by Mr. J. Sinel, who however did not 

 identify his interesting find till the publication, by Mr. I. C. Thompson, 

 of the description of a specimen of the same animal taken off Anglesey 

 in the autumn of 1887. Mr. Thompson at first believing the animal 

 to be new to* science, named it Cymbasoma herdmani (3) but later 

 on, having more material to examine, he recognized his animal to be 

 of the same species as Lubbock's. Since 1880, Monstrilla anglica 

 has appeared pretty regularly every year off Jersey during Aug. and 

 Sept., in sparing numbers. Mr. Thompson has also recorded a second 

 specimen from the Irish sea (5), and another from off Malta, while 

 one or two more have been taken on the south coast of England. 

 Apparently then, here in Jersey, we have been the most successful in 

 obtaining this rare animal. Indeed of late years we have been specially 

 so, for out of a small number of tow-nettings taken in Aug. and Sept. 

 of the last two years, we have picked out nearly 80 specimens. 



Normal Copepoda may be defined as minute crustaceans of 

 simple organization, having an elongated body clearly divided into 

 numerous rings or somites, and without the shield-like shell or 

 carapace that covers the anterior part of the body being double or 

 bivalve, having an anterior pair of antennas or feelers (properly 

 antennules) ; a posterior pair (the true antenna?) ; 3 pairs of 

 mouth organs (1 pair mandibles, 1 pair maxillce, and % pairs 

 of maxillipedes), and five pairs of two-branched, biramous, swimming 

 feet attached to the. anterior part of the body or cephalothorax. The 

 hinder end of the body consists of an abdomen of 5 somites bearing 

 no organs and terminated by a forked tail. 



