IOWA ACADEMY OF SC1E^'CES. 125 



The earthworm, clam and crayfish are of course standbys, and the only 

 point I might suggest here is to have an abundant supply of these preserved, 

 as it is sometimes difticult to secure these in abundance at just the time they 

 are wanted. It is naturally demoralizing to a class to be short of material, 

 and with classes numbering forty or fifty the question sometimes becomes 

 a serious one. This is especially true in case the time for these subiects falls 

 within a period of drouth when the earthworms may be out of reach except 

 in favored spots, the crayfislies hidden in some very moist corner, or, with 

 the clams, to be found only in some pool that has survived the drouth. Such 

 material may be kept fresh in good sized tanks or aquaria, or preserved in 

 alcohol; some at least should be prepared in the latter way for use in dis- 

 secting certain parts. I have a large cement lined tank sunk in the floor of 

 the basement of the building occupied by the laboratory, which is very con- 

 venient for keeping clams, crayfishes, frogs and fishes, and it also forms an 

 attractive feature, being as much sought for as the museum cases by visitors, 

 especially by children. 



I find in the vicinity of Ames that the common Differential Locust 

 {Melanophis differenlialis) forms one of the most available species for 

 laboratory work. It is much larger than the more common femur-rubrum, 

 hence more easily studied by the beginner and is more easily collected in 

 quantity than the large species of Acridium. 



For fishes I generally find it most convenient to order through the meat 

 market undrawn fishes of eight to twelve inches in length. Sometimes we 

 get fresh mackerel or other marine fishes, but more commonly lake or river 

 species. 



Snakes and turtles have to be secured as they turn up, but students 

 usually secure enough to answer the purpose. Turtles are not kept on the 

 market with us, and to order them from a distance is rather expensive. 



For birds, pigeons, or in case these are wanting, blackbirds or robins 

 serve the purpose. 



If classes are not too large the embryology of the chick forms a most 

 entertaining and instructive study, but the work is somewhat difficult to 

 manage except with students somewhat advanced, and even then it is best 

 not to attempt to direct too many at once. The eggs may be incubated 

 artificially, but about the most satisfactory way is to use a hen, especially if 

 a good, persistent setter is available. Sometimes one can be kept busy for 

 five or six weeks and in this time incubate a large number of eggs. 



For small mammal the most available, easily secured and satisfactory 

 with us is the striped ground squirrel [Spermophilus tridecemlineatus). 

 These are very abundant on the campus, may be caught very quickly by the 

 use of slipnoose cord and without any injury to any part of the body as 

 occurs with rabbits if shot. This Tuakes them available for injection or for 

 any treatment desired. Rats I have seldom used, as with us it is more 

 bother to secure them than squirrels, but of course rats, rabbits, cats and 

 dogs are used on occasion. It seems to me fully as well to use a species 

 different from the one described in the guide, if a guide is used, since it 

 throws the student on his own resources, incites comparative study and 

 prevents too close following of the guide, either in description or drawing, 

 in fact the main object of the guide is to ensure attention to all structures 

 that should be studied, and to avoid waste of material, in case the animal is 



