216 On the Study of Biology. [ April, 
chosen one — will be able to have a very fair conception of the 
structure of the whole. Ido not mean to say he will know that 
structure thoroughly, or as well as it is desirable he should know 
it, but he will have enough real knowledge to enable him to un- 
. derstand what he reads, to have genuine images in his mind of 
those structures which become so variously modified in all the 
forms of insects he has not seen. In fact, there are such things 
as types of form among animals and vegetables, and for the pur- 
pose of getting a definite knowledge of what constitutes the 
leading modifications of animal and plant life it is not needful to 
examine more than a comparatively small number of animals and 
plants. 
Let me tell you what we do in the biological laboratory in the 
building adjacent to this. There I lecture to a class of students 
daily for about four and a half months, and my class have, of 
course, their text-books; but the essential part of the whole 
teaching, and that which I regard as really the most important 
part of it, is a laboratory for practical work, which is simply a 
room with all the materials arranged for ordinary dissection. 
We have tables properly arranged in regard to light, microscopes, 
and dissecting instruments, and we work through the structure 
of a certain number of animals and plants. As, for example, 
among the plants we take a yeast plant, a Protococcus, a common 
mould, a Chara, a fern, and some flowering plant; among the 
animals, we examine such things as an ameeba, a Vorticella, and 
a fresh-water polyp. We dissect a star-fish, an earth-worm, a 
snail, a squid, and a fresh-water mussel. e examine a lobster 
and a eraw-fish and a black beetle. We go on to a common skate, 
a cod-fish; a frog, a tortoise, a pigeon, and a rabbit, and that takes 
us about all the time we have to give. The purpose of this 
course is not to make skilled dissectors, but to give every student 
a clear and definite conception, by means of sense-images, of the 
characteristic structure of each of the leading modifications of the 
animal kingdom; and that is perfectly possible, by going no fur- 
ther than the length of that list of forms which I have enumerated. 
If a man knows the structure 6f the animals I have mentioned, he 
has a clear and exact, however limited, apprehension of the essen- 
tial features of the organization of all those great divisions of the 
animal and vegetable kingdoms to which the forms I have men- 
tioned severally belong. And it then becomes possible for him 
to read with profit, because, every time he meets with the name 
of a structure, he has a definite image in his mind of what the 
