86 



The Canadian Field-Naturalist 



[Vol. XXXIII 



The fcot is capable of great extension as may be 

 observed if living shells are placed in a glass bowl 

 or aquarium. Cilia in the bronchial siphon, and 

 along the inner and cuter gills and mantle, induce 

 currents which bring diatoms and other minute 

 organisms contained in the water into contact with 

 the libial palpi, whence they pass into the stomach 

 to be in part elaborated for the preservation and 

 growth of the individual and the propagation of its 

 kind, and in part rejected through the excurrent or 

 cloacal siphon. 



Unlike the Un'ionidae in which each individual 

 is dioecius, that is, either a male or a female, as is 

 the case also with our native oyster (O. v'lrgin'ica, 

 Gmelin), though not, strange to say, with its Europ- 

 ean relative (O. edulis, Linn.), 5. sulcatum, like all 

 other species of the Sphaeriidae, is monoecious, or 

 produces both sperm and ova within the same shell. 

 However, it is net harmaphrcditic in the way that 

 many, if not all, pond and other snails are herma- 

 phroditic. In their case, while each animal is per- 

 fectly bisexual, the conjunction of two individuals 

 is requisite for fertilization. In the Sphaeriidae, 

 en the other hand, the process of fertilization is 

 similar to that which takes place within the closed 

 keel of the pea blossom and other legumes. Cross 



fertilization is impossible naturally, and could not 

 be induced artificially were another Mendel to arise. 

 The reproductive organs are located behind the 

 stom.ach, and consist of racemose glands, the an- 

 terior of which produces sperm, and the posterior 

 ova. A common genital duct leads in the cloacal 

 chambers of the inner gills, where the young reach 

 before birth, in the case of this species, a length 

 of seven or eight millimeters, or nearly half that of 

 the father-mother.' If living shells are left for a 

 day or two in water that is warmer or colder than 

 that of their usual habitat, they will, ordinarily, be 

 found to have produced a large number of nepionic 

 young. These should be separately boxed and 

 labelled with the name of the parent and will be 

 found very useful when the collector is trying to 

 identify shells which are no larger when aged than 

 some Sphaeria are at birth. 



(To be continued) 



5The reproduction and growth of S. .sulcatum 

 are treated at length by Ralph J. Gilmour in The 

 .N'autilus, Vol. 31 (iyi7), pp. 16-28. 



Note. It is my intention to place in tlie Museir.Ti 

 of the Geological and Natural History Surve> at Ot- 

 tawa specimens of the forms and varieties of S. 

 sulcatum, and of the species mentioned in the con- 

 tinuation of this paper, of which I possess 

 iiuplicates. 



FIELD STUDY OF LIFE-HISTORIES OF CANADIAN MAMMALS. 



By Rudolph Martin Anderson, Biological Division, Geological Survey, Ottawa. 



A recent and timely publication of the United 

 States Department of Agriculture'- calls attention 

 to the gaps in our knowledge of the habits of many 

 of the commoner species of mammals. The study 

 of birds has been developed so extensively in a 

 popular way in recent years through the Audubon 

 Society movement, local bird clubs, and nature 

 studies in the public schools, as well as technically 

 by the scientific ornithologists, that the objects and 

 methods of bird study have become fairly well 

 known throughout the country, and the economic 

 importance and aesthetic and sentimental value of 

 bird life are becoming matters of common 

 knowledge. 



The study of mammals, though not less im- 

 portant in many ways, has not been developed so 

 broadly or systematically. The study of the com- 

 parative anatomy and physiology of the major 

 mammalian groups, through their closer relation 



iPublished by permission of the Geological 

 Survey, Ottawa, Canada. 



^Suggestions for Field Studies of Mammalian 

 Life-Histories. By Walter P. Taylor, Assistant 

 Biologist. September, 1919. U.S. Department of 

 Agriculture. Department Circular 59. Contribu- 

 tion from the Bureau of Biological Survey, E. W. 

 Nelson, Chief; pp. 1-8. 



to the human subject, has received close attention, 

 but the relations of species to one another and to 

 their environment, and their life-histories, are un- 

 doubtedly less well known than the like relations 

 of birds. It is true that the horse, cow, sheep, 

 pig, and a few other mammals have been domest- 

 icated, but few attempts have been made to dom- 

 esticate ether species except in a sporadic way. 

 A rather extensive but scattered literature has been 

 developed concerning the deer, elk, moose, bison, 

 antelope, and other large game animals, which 

 are of interest to the sportsman. Unfortunately, 

 this in many cases consists principally of the lore of 

 hunting field and methods of capture, and what 

 may be termed their more intimate history has been 

 neglected until many of the species have been ex- 

 terminated over most of their former ranges, and it 

 is forever too late to obtain complete data in regard 

 to these animals' relations to their primitive con- 

 dition. Where efforts have been made, often too 

 late, to conserve a remnant of these animals, to 

 replenish the game of the sportsman, add to the 

 food supply, or for other practical or sentimental 

 reasons, it is found that there is a lamentable lack 



