346 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Use of Slime-threads in Marine Gastropods.* — N. Colgan has 

 observed ten species climbing by the help of suspensory slime-threads. 

 The animals can drop from the surface, can hang suspended, and can 

 climb up again. The species studied were : Runcina hancocki, Lima- 

 pontia nigra, Doto coronata, Eolis farrani, E. drummondi, Skenea 

 planorbis, Rissoa striata, R. parva, and R. cingillus. In the young of 

 the common bivalve Modiolaria discors the use of slime-threads was 

 also seen. On a vertical surface of plate-glass Rissoa striata can crawl 

 an inch in three minutes, Trochus zizyphinus an inch in one minute, 

 Eotis farrani and E. drummondi, at the dizzy rate of an inch in fifteen 

 seconds and thirteen seconds respectively. 



5. Lamellibranchiata. 



Striped Muscle in Mantle of Lamellibranchs.f — W. J. Dakin has 

 found striped muscle in the mobile mantle edge of Pecten jacobseus and 

 P. opercularis. The striation is not oblique like the cardiac and 

 adductor muscles of most Lamellibranchs, but apparently transverse 

 like the adductor muscle of Pecten, though perhaps not quite so regular. 

 " It is interesting to note that the muscles which show such an obvious 

 striation are engaged in rapid movements, which are also organised and 

 related to the closing and opening movements of the shell in swimming, 

 another case, therefore, of the connection between striation and rapid 

 contraction and relaxation." 



Pecten. :f — W. J. Dakin has prepared an admirable memoir on Pecten. 

 He discusses the animal's behaviour and gives a full account of its 

 structure. In connection with some of the organs the physiological 

 side receives careful attention. It is shown, for instance, that the 

 digestive gland contains proteolytic, amylolytic, and lipolytic ferments. 

 A detailed account is given of the eyes, in regard to which there has 

 been much confusion. The development of the animal is dealt with 

 very briefly. The memoir concludes with a chapter on the economic 

 importance of the scallop, both for human food and for bait. 



Life-history of Canadian Oysters.§ — J. Stafford gives an account 

 of some of the larval stages he has found in the plankton at various 

 depths in Richmond Bay, Prince Edward Island. The free-swimming 

 period is probably close on a month. The larvae feed and grow while 

 free- swimming, and pass through a straight-hinge stage to an umbo 

 stage. Normal fixation takes place when the larval shell is about 

 0*38 mm. in length, and then the spat period begins. A metamor- 

 phosis occurs with loss of larval organs (velum, foot, eye-spot, otocysts, 

 etc.) and growth of new organs (spat-shell, additional gills, palps, etc.). 

 The larval shell is asymmetrical, as is also to some extent the contained 

 body. Some account is given of the foot, the pedal ganglia, the oto- 

 cysts, the eye-spots, and the byssus gland, and some questions of 

 economic importance are discussed. 



* Ann. Nat. Hist., iii. (1909) pp. 354-62. 

 t Anat. Anzeig., xxxiv. (1909) pp. 227-30 (5 figs.). 



t Liverpool Marine Biology Committee Memoirs, No. xvii. (1909) pp. 1-36 

 (9 pis.). § Amer. Nat., xliii. (1909) pp. 31-47 (1 pi.). 



