112 METHODS or COLLECTING AND PRESERVING 



Hydrocorallinm. — This group includes the llillepo'i'idce and 

 Stylasteridce. Any observations on the living polyps would be 

 valuable. It would be of special interest to discover the minute 

 medusiform individuals which escape by rupture of the wartlike 

 elevations which stud the surface in certain parts. 



Moseley's method of sudden killing of specimens with expanded 

 polyps by means of hot corrosive sublimate should be tried. 



hijihonojjhora. — These animals are very difficult to preserve satis- 

 factorily, owing to the tendency of the swimming bells, polyps, and 

 tentacles to break away. The method of killing and fixing with 

 osmic acid, washing in fresh-water, and grading into alcohol, 

 may be adopted (see below, Medusce). For other means of 

 preserving, the collector is referred to Signor Lo Bianco's paper 

 on the Naples methods, or to the cupric-sulphate method of Bedot, 

 quoted by Mr. A. B. Lee.* 



Medusce. — Medusae in many instances represent merely one phase in 

 a series of transformations undergone by an organism in the course 

 of its life-history. 



Many of the smaller forms are budded off from fixed Hydroids. 

 In the case of some of the larger forms (e.g. Aurelia) the oval free- 

 swimming embryo settles down and becomes a minute white polyp 

 with long tentacles ; the polyp divides transversely so as to resemble 

 a pile of saucers ; the latter become free, and ultimately develop into 

 the adult form. It is important to obtain all these stages. 



The discovery of new forms of fresh-water Medusae would be an 

 event of the greatest interest. 



Kecently Mr. E. T. Browne t has obtained good results in pre- 

 serving the smaller kinds of Medusa3 by using formalin, after killing 

 and fixing with a saturated solution of picric acid. The contents of 

 the towing-net are emptied into a glass vessel of sea- water. By 

 means of a pipette any particular specimen is removed to a watch- 

 glass of sea- water. Five drops of hydrochlorate of cocaine are 

 added, and in a few minutes another five or ten drops. When 

 the Medusa is motionless and has its tentacles extended, any 



* " Microtomist's Vade Mecum," 5th edit., ]900, p. 487. 

 . t E. T. Browne, " Proc. Liverpool Biol. Soc," 1895, IX., p. 245 ; " Proc. Zool. 

 Soc," 1896, p. 461 ; and " Journal of Biometrika," 1901, Vol. I., p. 108. 



