258 CHAS. W. IIARGITT, 



were made at varying seasons, chiefly June, July and August at Woods 

 Holl and during May and June at Naples, and in each case during 

 at least two years, so that it may be safely assumed to represent 

 average conditions of growth, maturity, etc. The preservation of 

 material was under direct personal observation and in all cases upon 

 perfectly fresh specimens and by a wide range of reagents, including 

 hot sea-water, the various forms of Mercuric chloride, with and 

 without acetic acid, and used both hot and cold ; the various picric 

 acid preparations, Flemming's solutions, weak and strong, Hermann's 

 solution, Perenyi's solution. The various preparations of formol, pure 

 alcohol alone and with such reagents as formol and Mercuric chlorid 

 in solution. While good fixation was obtained by both Hermann's and 

 Flemming's solutions, subsequent staining proved difficult and unsatis- 

 factory. Upon the whole the best results were obtained from fixation 

 with a strong alcoholic solution of Mercuric chloride. The several 

 picric acid formulae have proved unsatisfactory in the fixation of 

 coelenterate material, whether of hydroids, medusae, or their ova. 

 Depending in my earlier collections upon the general repute of this 

 reagent they were later found, greatly to my surprise and regret, to 

 be almost worthless. Perenyi's solution gave only fairly satisfactory 

 fixation. I have found in some cases excellent results from a 10 "/^ 

 solution of formol in sea-water, tho prepations in this medium were 

 not constant, nor did stronger solutions prove any more satisfactory. 

 In some cases a mixture of equal volumes of absolute alcohol and 

 glacial acetic acid gave good results. 



Origin of the Sex-cells. 



Since the announcement of Cavolini (1785) that Hydroids pro- 

 duced eggs, although what he at that time supposed to be such were 

 probably larvae, the subject of sex-cells has been a matter of extended 

 interest and research. The researches of Eiirenberg, Siebold, Sars, 

 Steenstrup and Dujardin, established the fact and law of the "alter- 

 nation of generations". 



Van Beneden (1843) seems to have earliest directed attention 

 specifically to the question of the origin of the sex- cells in work done 

 on Hydroids and announced that the eggs originate in the cells of 

 the endoderm, while spermatozoa arise in the ectoderm. He proposed 

 this as probably true throughout the animal kingdom, an illustration 

 of hasty generalization from extremely limited data, and with the 

 futile results usual in such cases. 



