vi PREFACE 



superior for laboratory purposes in some ways since the 

 specimens are usually mature, which allows a full dissec- 

 tion of the urogenital system. The body form of the 

 skate is highly specialized, which makes necessary the in- 

 troduction of demonstration material to illustrate the gen- 

 eralized form. This body shape, however, makes the skate 

 much easier to dissect, since it naturally rests in a suitable 

 position and does not need to be fastened to the dissection 

 board. 



The laboratory dissection of the skate conforms with the 

 current textbooks of vertebrate zoology, since it deals with 

 a specimen not discussed or figured in any detail yet serves 

 as an excellent example for comparison with the textbook 

 material on related forms, making possible the legitimate 

 and desirable use of such books in the laboratory. 



Besides these fundamental points in its favor the skate 

 is easier to obtain and to store. The cost of skates, accord- 

 ing to the prices current with supply companies, is almost 

 one-half that of immature sharks. Only one singly in- 

 jected specimen is needed for this manual. 



Figures of the venous system and the skeleton are in- 

 cluded since these systems are most difficult to dissect. 

 The figure of the venous system is unlabeled and is in- 

 tended to aid in the student's organization of this system. 

 The skeleton of the average specimen is badly injured dur- 

 ing dissection but much may be determined with the aid of 

 the figure. 



Numerous laboratory guides, outlines and textbooks have 

 been consulted and their suggestions reworked into the 

 present manual during the dissection of many skates in 

 our laboratory. Considerable material has been utilized 

 from ** Zootomy" by T. J. Parker, ''Outlines of Zoology," 

 by J. A. Thompson; *'A Laboratory Manual for Compara- 



