STRUCTURE OF THE T,ARVA OF SPONGILLA LAOUSTRIS. 443 



The staining solutions which were used had the following 

 composition : 



90 c.c. distilled water saturated with aniline oil. 

 10 c.c. absolute alcohol. 

 1 gramme of the stain (safranin or gentian violet). 



(c) Gentian Violet. — The sections were left in the stain- 

 ing solution for fifteen minutes, and were then subjected to 

 the action of absolute alcohol and clove oil until they were 

 sufficiently diflferentiated, being then mounted in Canada 

 balsam as usual. The solution used for staining purposes in 

 this case was the same as in the previous method. 



Though the above are the chief methods which have been 

 used, several other methods have been tried, both in the way 

 of combining the above stains in a different manner and 

 of using other staining solution not mentioned above. 



The following may serve as a few examples of the numerous 

 combinations which have been tried : — first, safranin, followed 

 by gentian violet and orange G; secondly, Bismarck brown, 

 followed by malachite green ; thirdly, iodine green, followed 

 by fuchsin S ; and lastly, haematoxylin, followed by orange G 

 or eosin or picric xylol instead of fuchsin S. 



The above enumeration of the staining methods which 

 have been tried suffices to show that no trouble has been spared 

 to test the correctness of the conclusions arrived at in this 

 paper. 



III. Comparison of the Above Account with those 

 OF Previous Authors. 



When I embarked upon the study of the structure and 

 metamorphosis of the larva of Spongilla I hoped to be able to 

 show that one or other of the accounts which had already 

 been published was in the main correct. As I had no theory 

 whatever to uphold, I started on my work with an open mind. 

 However, I never expected that the result of my work would 

 be to show that nearly all the accounts were in the main 

 correct, though they were all incomplete. 



VOL. 42, PAET 4. NEW SERIES. HH 



