The Ottawa Naturalist 



to me. Probably few Ottawa naturalists have had the opportunity of 



studying these wonderful little creatures, and I venture, therefore, to 

 present a few notes on their structure and peculiarities. 



They are crustaceans, of the order Phyllopoda, suborder Branchi- 

 opoda. The body, which is of a glassy transparency, is about half an 

 inch long, the head being very distinct, though there is no line of 

 demarcation between the thorax and abdomen. The eyes, an ten rse, 

 limbs, heart and forked tail, when examined through the microscope, 

 are very beautiful . They are typical Entomostraca, for the body is 

 divided up into segments. The anterior antenna: are short and delicate 

 and difficult to distinguish. In the male the head is large, broad, and 

 the posterior antenna; are converted into claspers, having the base very 

 thick and massive, while the tip is knobbed or raiher hooked. The 

 eyes are very remarkable and quite unlike any other crustacean, so low 

 in zoological position. Carl Gegenbaur, in his "Elements of Compa- 

 rative Anatomy," draws special attention to the unusually interesting 

 character of the eyes. The Entomostraca, as a rule, possess very 

 simple eye spots, but in the Phyllopods, as Gegenbaur states, " we meet 

 with a facetting of the inner surface of the cuticle covering the eye, the 

 facet- corresponding to the crystalline cones." 1 he German anatomist 

 further points out " by their power of movement, and their position 

 immediately below the chitinous carapace the eyes of the 

 Branchiopoda form an intermediate step towards those in which the 

 chitinous carapace takes a more direct share in forming the optic organ." 

 Further, the position of the eye, on a stalk-hke process (in Anemia and 

 Branchipus) presents a point of affinity to the higher crustaceans, such 

 as lobsters, crabs, etc., which possess projecting stalked eyes. 



The last segments of the body form a long slender tail, the ter- 

 minal fork being exquisite in appearance, for under the microscope it is 

 like burnished gold, and studded with innumerable glassy haiis. In 

 front of the tail, the body is furnished with a large number of limbs, so 

 in dified as to perform the double function of locomotion and respira- 

 tion. They are virtually gill feet. The heart is a long tube, made up 

 of a series of chambers, and, as is usual in Arthropods, it is dorsal. 

 I he ' in ulation of the blood, driven by this pulsating heart tube in the 



