618 



SCIENCE 



[N. S. Vol. XXIX. No. 746 



principally in Soutli America, Asia and 

 Africa. 



Althougli the parasite has been known for 

 more than half a century, very little impor- 

 tance was attached to it until within the last 

 decade. As knowledge of these forms has 

 recently advanced, so have they become very 

 important, not only to the physician on ac- 

 count of their role in the etiology of disease, 

 but also to the zoologist who is desirous of 

 knowing their finer structure, their life his- 

 tory and their genetic affinities. 



One of the important phases of the article 

 is a discussion of the method of transmission 

 of the parasite. Doffein points out that there 

 are three probable modes of transmission. 



The first mode is by means of cysts or 

 spores. In such cases it would be necessary 

 for the parasites to wander through the walls 

 of the blood-vessels out upon the skin or 

 mucous membrane and there form cysts. 

 They must then be taken up with dust, water 

 or food by an intermediate host and be carried 

 to the vertebrate host. At present no facts 

 are known to support this theory, except that 

 certain authors have described stages in the 

 blood and internal organs, which they inter- 

 preted as cysts. But these are probably noth- 

 ing more than degeneration stages. 



The second method is through coitus, as is 

 the case with Spirochseta and the trypano- 

 some causing dourine. Doflein is of the opin- 

 ion that this mode of transmission may be 

 possible in all trypanosomes, and hence re- 

 gards it as an important point to be investi- 



The third method is the passive transmis- 

 sion through the agency of blood-sucking in- 

 vertebrates. Experiments show that insects 

 are capable of passively carrying the trypano- 

 somes from an infected to a sound patient. 

 Since the work of Schaudinn (1904) on the 

 transformations of the owl trypanosome in 

 the stomach of the mosquito, investigators 

 have thought that the trypanosome must pass 

 through a complicated life-cycle in an inver- 

 tebrate host. Setting out with Schaudinn's 

 work before them, they have tried to fit their 

 discoveries to his interpretations. They have 

 searched for male and female forms, believing 



that there must be a life-cycle similar to 

 malarial forms in the mosquito. But no one 

 has ever yet seen male and female, if they 

 exist, in process of conjugation, and so the 

 insect is known only to be a passive carrier 

 of the infection. Leroy D. Swingle 



Nebraska Wesletan Univeesixy, 

 University Place, Nebb. 



The Study of Nature. By Samuel Christian 

 ScHMUCKER. Pp. 315, illustrated. Phila- 

 delphia, J. B. Lippincott and Co. 1908. 

 $1.25. 



This latest addition to the long list of books 

 designed to guide teachers of nature study 

 will, like many of its rivals, give much help; 

 but still leaves the most pressing problems of 

 elementary school nature study just where 

 they were before its publication. This fact is 

 mentioned not in criticism, but simply to fore- 

 warn those who eagerly expect each new book 

 on nature study to make some decided ad- 

 vance towards complete establishment and suc- 

 cessful teaching of the subject in all our ele- 

 mentary schools. For such a golden age of 

 nature study we have as yet at most only a 

 prophetic vision. 



In the first chapters dealing with the prin- 

 ciples of nature study the author follows the 

 most advanced stage of the nature study move- 

 ment when he urges as essential the observa- 

 tional study of natural things, as far as pos- 

 sible, in their natural relations and chosen for 

 their commonness and abundance rather than 

 for their rarity. 



In the chapter on The Real Purpose of 

 Nature Study the author agrees with many 

 other writers in urging nature study as for 

 many individuals a valuable addition to the 

 general culture which is valuable for avoca- 

 tion rather than for the main business of life. 

 Also be believes in practise in accurate ob- 

 serving and stating results' as decidedly effec- 

 tive in establishing firm character, and in na- 

 ture study as a guide to a religious attitude 

 towards nature. All this agrees with the ex- 

 perience of many naturalists, but the doubting 

 educators who have had no experience in 

 scientific study will continue to regard these 

 purposes as vague and not convincing. The 



