APPENDIX. 



473 



to supply oxygen. The whole development from ovum to 

 late tadpole-stage can be watched, and a much better notion 

 of the process obtained than from any written account so 

 far, that is, as external form goes. A tadpole affords good 

 practice in fine dissection. 



If the student can gain access to an artificial incubator, 

 he would do well to study the early development of the chick 

 by taking eggs at the end of one, two, three, and four days 

 of incubation (and as many other stages as he pleases), and 

 carefully opening them in a dish of warm water. The egg 

 should be laid on its side, and the part of the shell that lies 

 uppermost carefully removed. 



The making of sections of tadpole or chick is beyond 

 the means of the solitary worker, but if he can get 

 prepaied sections from a dealer he should examine them 

 carefully. 



For the rabbit, pregnant females can be easily obtained 

 and dissected. The placenta and other extra-embryonic 

 structures can be examined ; and if the embryos are well- 

 advanced, they may be hardened in formalin, and sections 

 cut with a sharp scalpel. Fig. 2 was drawn from embryos 

 treated in this way. 



FURTHER STUDY. 



Finally there may be among the readers of this volume 

 many who will be anxious to extend their knowledge of 

 Zoology in general, or of the particular types we have taken. 

 For further practical work the London University syllabus 

 for Honours in Intermediate Science, and that for the Pass 

 B.Sc. examination, afford a good selection of types to study. 

 These can be obtained from the dealers already mentioned, 

 who issue price lists. 



For additional reading, Parker's Elementary Biology (Mac- 

 millan) is an admirable work, covering both animal and 

 vegetable kingdoms. Parker and Has well's Text- Book of 

 Zoology (Macmillan, 2 vols.) is unquestionably the best and 

 most complete English work on Zoology in general. For 

 those who desire a smaller work of the same kind, no better 

 one can be recommended than Thomson's Outlines of Zoology 

 (Pentland). - 



ZOOL. 



