NOTES AKD MEMORANDA. 303 



manner. In the year 1872, wliile studying living UliynclioneUa in 

 the St. Lawrence, Mr. E. S. Morse observed * a specimen protrude its 

 arms to a distance of four centimetres beyond the anterior borders of 

 the shell, a distance nearly equalling twice the length of the shell. 

 This year he again had an 02Ji)ortunity of studying it in Hakodate, 

 Yesso, and again observed the same features. Specimens lying on the 

 bottom of a glass dish protruded their arms a short distance, and 

 remained in this position for hours. The movements of the arms 

 were very sluggish, th(jugh the cirri were constantly in motion. Some- 

 times the shells closed upon the arms before they were retracted. 

 Lingula has the power of partially protruding its arms, as he has 

 repeatedly observed in North Carolina and Japanese species. Tere- 

 hratulina can also partially protrude the cirri. 



Eye of the Lamellibranchiata. — It is peculiarly interesting to 

 observe that the " visual purple " which the researches of Franz Boll 

 and Kiihne have made known to all microscopists is to be observed in 

 the eyes of some of the Invertebrata ; Professor Hensen calls atten- 

 tion to this matter ■]• in reference to certain observations made by 

 Krukenberg on the eyes of the Cephalopoda. Hensen has observed in 

 Pecten Jacohoeus, that the layer of rods is distinguished from the 

 surrounding parts by its coloration. Krukenberg in his notice con- 

 cludes that in the Cephalopoda the colour is persistent, but in Pecten 

 Hensen noted its ra2)id disappearance. Hensen also corrects some 

 of his observations on the eye of this Lamellibraucb, which were 

 published a few years ago. 



Foot of the TTnionidae. — J. Carrier e bas been making some obser- 

 vations J on the foot of the Unionidee, which have led him to the 

 following conclusions : the injections of the lacunae and blood-vessels, 

 which one is, at times, able to make through a cleft at the margin of 

 the foot, are effected by the destruction of fine tissues ; this cleft does 

 not, that is, communicate with the vascular system, but is the aper- 

 ture of a closoil, and variously developed gland. This organ often 

 contains a yellow secretion. The various stages of its development 

 are indicated, and it is pointed out that it is greatly reduced in Unlo, 

 where indeed it may be merely represented by a short ciliated canal. 

 It is concluded that it represents a rudimentary byssus gland, and 

 the author promises more complete details. 



"Digger" Mollusc and its Parasites. — The little digger, Donax 

 fossor, represents a countless mass of life off Cape May, New Jersey, 

 large areas looking like barley grains lying on a malting floor 

 when the tide retires. It gets imcovered by the breaking surf and 

 instantly reburies itself with its powerful foot when the waves retire. 

 The siphons are long and active, looking like so many wriggling 

 worms. Although the prey of shore birds and fishes, and beset with 

 parasites, they lie so thick as even to interfere with one another in 

 burying themselves. The liver of these bivalves is always found 



* 'Am. Jour. Sci. and Arts,' xvii. (1879) 257. 



t ' Zool. Anzeiger,' i. 30. + Ibid. (1878) 55. 



