Makch 1, 1918] 



SCIENCE 



223 



amount of space. In the case of the latter, 

 many photographs aid in familiarizing the 

 reader with the forms of flowers and foliage. 

 Notes on mammals and birds are almost ab- 

 sent. A single instance of a bird feeding upon 

 lepidoptera was noticed. On the other hand, 

 copious notes were made on the natives, their 

 customs, mode of life, houses and villages. 

 But the matter relating to dragonflies, the dis- 

 covery of the various forms and the rearing of 

 their larvse, stand out from all the rest of the 

 text. In dealing with this phase of research, 

 the enthusiasm is distinctly greater, the dic- 

 tion more pleasing, and the treatment more 

 thorough. 



The text presents many readable descrip- 

 tions of scenery and of unexpected conditions 

 in this tropical country. Such a one is the 

 strawberry field with its amazing amount of 

 delicious fruit, shaded by tall rose trees. And 

 the last chapter has a most vivid narrative of 

 a disastrous earthquake in which the whole 

 city of Cartago was ruined and several hun- 

 dred people killed. The authors fortunately 

 escaped with their notes and photographs. 

 They go on to recount : " The falling wall car- 

 ried with it the tumbler shelf so that the 

 larvse, the rearings of many mouths, were 

 all killed — with one extraordinary exception. 

 A bottle of new Cora larvae which P. brought 

 with him the evening before from Juan Vinas 

 — the rarest thing we had — was found on the 

 floor, unbroken and with the larvse alive ! " 



In addition to the well-made index there are 

 several appendices dealing with the itinerary, 

 temperature and rainfall records, a sunmiary 

 of papers published in connection with the 

 collections made on the trip, and a systematic 

 list of plants and animals mentioned. As this 

 latter has the page references, the contents of 

 the volume are thus made still more available 

 for reference. The authors are to be sincerely 

 congratulated on having saved their incidental 

 notes and observations from oblivion. Such 

 work can not fail to add to any breadth of 

 generalizations in their own more narrow 

 field of special, intensive work, and sets a 

 standard for other expeditions which it is 

 hoped will often be equalled or surpassed. 



" The Voyage of the Beagle " is bearing late 

 fruit and should be a stimulus to all such ef- 

 fort in the future. 



Wm. Beebe 

 New York Zoological Park 



SPECIAL ARTICLES 



THE EFFECT OF OMNIVOROUS AND VEGE- 

 TARIAN DIETS ON REPRODUCTION IN THE 

 ALBINO RAT 



An experiment, now in its fifth year, is 

 being carried on to show the effect of a vege- 

 tarian diet as compered to an omnivorous diet 

 on reproduction in the albino rat in regard to: 



1. The relative number of litters produced. 



2. The relative nimiber in the litter. 



3. The relative frequency of producing 

 litters. 



4. The relative ratio of the sexes. 



3. The relative vitality and growth of the 

 young. 



6. The relative longevity and general ap- 

 pearance. 



7. The relative age at which breeding be- 

 gins and ceases. 



8. The general effect upon successive gen- 

 erations. 



9. Sterility test; to determine whether it 

 is the male or the female which is rendered 

 impotent. 



The number of pairs constantly under ob- 

 servation was 40. Approximately 20 of these 

 pairs were restricted to a vegetarian diet and 

 the remaining, used for control, were given 

 the same vegetables with some form of an- 

 imal food added. As soon as one of a pair 

 died the other was remated. Or when they 

 became too old to breed they were discarded 

 and the cage restocked. 



The results and conclusions so far reached 

 may be summarized as follows: 



If only those pairs which produce litters 

 are taken into consideration the average num- 

 ber of litters per pair for the omnivorous 

 group is 3.73 and for the vegetarian, 1.93. 

 But when the whole group of matings are con- 

 sidered we find that 11.5 per cent, of the 

 omnivorous and 55.9 per cent of the vege- 

 tarian pairs failed to reproduce. If these are 

 considered, the average number of litters is 



