NATURE-STUDY. xv 



the opening to the lung. In the shell-bearing snails it 

 is just under the edge of the shell, and usually invisible 

 unless you look for it. They all need air as surely as 

 you and I." 



Dr. Leidy could teach nature study, and the reason is 

 obvious. The alleged "teacher" who called the slug "a 

 nasty thing; throw it away," could not, and the reason 

 is likewise obvious. 



In the "Concluding Remarks" to his magnificent mono- 

 graph on "The Fresh- Water Rhizopods of North Amer- 

 ica," this same Dr. Leidy says: 



'• The objects of my work have appeared to me so beautiful, . . . 

 and so interesting as indicated in their history, which forms the accom- 

 panying text, that I am led to hope the work may prove to be an incen- 

 tive, especially to my young countrymen, to enter into similar pursuits. 

 The study of natural history in the leisure of my life, since I was fourteen 

 years of age, has been to me a constant source of happiness, and my ex- 

 perience of it is such that, independently of its higher merits, I warmly 

 recommend it as a pastime which, I believe, no other can excel. At 

 the same time, in observing the modes of life of those around me, it 

 has been a matter of unceasing regret that so few, so very few people give 

 attention to intellectual pursuits of any kind. In the incessant and neces- 

 sary struggle for bread, we repeatedly hear the expression that ' man shall 

 not live by bread alone,' ard yet it remains unappreciated by the mass of 

 even so-called enlightened humanity. In common with all other animals, 

 the engrossing care of man is food for the stomach, while intellectual food 

 too often remains unknown, is disregarded or rejected. 



"' Gning fishing ? ' How often has the question been asked by ac- 

 quaintances, as they have met me, vrith rod and basket, on an excursion 

 after materials for microscopic study. "Yes ! ' has been the invariable ans- 

 wer, for it saved much detention and explanation, and now, behold, I offer 

 them the results of that fishing. No fish for the stomach, but, as the old 

 French microscopist, Joblot, observed, 'some of the most remarkable 

 fishes that have ever been seen,' and food fishes for the intellect. 



"To my pupils, both of the University of Pennsylvania and Swarth- 

 more College, but especially the boys and girls of the latter, who have at- 

 tended my lectures on natural history, the work will be of interest, as 

 they will recognize in its illustrations many of the simplest forms of animal 

 life vyith which they have been made familiar through my instruction. In- 

 deed, in the course of preparation of the book I have always had my 

 pupils in mind, and I shall be glad if it serve as an additional aid to their 

 studies." 



