338 MARINE INVERTEBRATE FAUNA OF PLYMOUTH. 



specimen. The discovery of these specimens confirms in an interest- 

 ing manner the prediction of Norman and Stebbing concerning the 

 secondary sexual characters of the adult male of this species (Trans. 

 Zool. Soc, xii, p. 123). 



A specimen of Idotea parallela (B. and W.) was dredged on 

 June 8th in Cawsand Bay. It presented a curious appearance when 

 alive, for it was inhabiting a piece of the stem of a dead Zostera 

 plant, which it carried about with it like a caddis-worm in its tube. 

 The thick^ soft, white antennae of this species are very characteristic, 

 and were at first much more suggestive to me of the tentacles of a 

 Polychtete than of Crustacean appendages. 



Two species of Arcturus have been frequently taken among the 

 filamentous Algse to which they cling. Their peculiar form, colour, 

 and habits of fixation render them excellent examples of protective 

 adaptation. 



The Cumacea are still under examination. Pseudocuma cercaria 

 is abundant ; and Iphinoe trispinosa, a species of Diastylis, and other 

 forms, are plentiful in their respective localities. 



Of the Schizopoda, Macromysis flexuosa [chamseleon of authors) has 

 been very abundant this summer. Each time that I visited the 

 estuary of the Yealm during July and August I found it at low tide 

 swimming in countless myriads close to the water's edge. It is inter- 

 esting to watch the behaviour of this Mysis when placed in a tank con- 

 taining some of its piscine enemies. It is a good match for the sharp- 

 sighted but too eager wrasses, and, when pursued, generally manages 

 to escape from them by darting swiftly away in an irregular zigzag 

 manner ; but the John Dory catches the Mysis easily by moving 

 stealthily towards them by means of its almost invisible fins, and, 

 when within reach, suddenly projecting its huge protrusible jaws, 

 and sucking in the unsuspicious shrimps. The middle of July marked 

 the height of the breeding season of this species. 



The same may be said of Schistomysis spiritus, which was taken 

 in considerable numbers in Whitsand Bay on July 15th, at which 

 date all the individuals were of large size, and the marsupial pouches 

 of the females were full of embryos. By August 3rd almost all the 

 large individuals had disappeared, and the bottom net brought up 

 thousands of small Schizopods, consisting chiefly of the young of 

 this species. Along with them, however, were adult specimens of 

 Gastrosaccus sanctus, and of a small robust species of Schistomysis, 

 allied to 8. arenosa, which seems to be new to science. 



On the night of September 21st the Mysidae Gastrosaccus Nor- 

 mani and Siriella jaltensis {8. crassi/pes, G. 0. Sars) were taken in 

 the surface-net in about equal numbers (principally males). The 

 former species was taken by the '' Porcupine " in 1869, and by 



