218 Chas. W,. and G. T. Hargitt. 



The various features of larval development were followed almost 

 continuously during the entire summer, a brief preliminary report 

 of which was published in the American Naturalist (1902 b, pp. 

 555-559). Unfortunately the material obtained at this time was 

 deficient in the earlier stages of egg development, especially those 

 relating to maturation, fertilization and early cleavage. Attempts 

 were repeatedly made at subsequent times to secure the desired 

 material for completing the problem, but with only partial suc- 

 cess; and it was not till the spring of 1908, in April, that the 

 junior author fortunately succeeded in obtaining a fairly adequate 

 supply for certain of the missing phases. He has accordingly, 

 been associated in the present work of carrying forward the problem 

 to a degree of completion which would have otherwise been more 

 or less impracticable, and is chiefly responsible for the cytologi- 

 cal part of the paper. 



Material a^d Methods 



The earlier material was obtained in July, 1901, from a few 

 specimens of medusae which had apparently, drifted into the har- 

 bor at Woods Hole, and were bearing ripe gonads, or rather 

 embryos in early stages of development. The occurrence of the 

 specimens at this time, and in this condition, would seem to be 

 more or less unusual, the usual breeding season for this medusa 

 being in April and early May in this region. But as will be men- 

 tioned in another connection, there are known to be many varia- 

 tions and exceptions to this rule. As already intimated, the 

 material was quite abundant so far as certain stages were concern- 

 ed. Unfortunately, however, the methods employed in fixation 

 of the material, chiefly picro-sulphuric and picro-nitric, reagents 

 then much in vogue, were found to be almost worthless so far as 

 these eggs were concerned, and as a consequence no satisfactory 

 cytological results were obtained. Later material was fixed in 

 various ways several of which proved most excellent, among which 

 Bouin's fluid and Zenker's seemed to give the most uniform type 

 of fixation, and gave no subsequent difficulty in staining. We also 

 obtained during the current summer at Harpswell several ripe 



