356 L. DONCASTER. 



Attempts to obtain eggs from Sagitta minima and Spa- 

 della draco were unsuccessful. 



At Naples the eggs were generally preserved with con- 

 centrated corrosive sublimate^ to which a small portion (about 

 5 per cent.) of acetic acid was added. This method also gave 

 excellent results with the young after hatching; some of 

 these were also preserved with osmic acid^ followed by 

 Miiller's solution for a day or two. The latter method was 

 more successful with the advanced young when the tissues 

 had already become differentiated ; for purely embryonic 

 tissue it gave poor results. Some of the young were also 

 preserved in a solution of potassium bichromate, to which a 

 little acetic acid was added, a method which gave results on 

 the whole similar to those produced by sublimate and acetic 

 acid. 



In most cases the material was embedded in celloidin and 

 then in paraffin, and cut in sections '004 or "005 mm. thick ; 

 this method facilitated the orientation and gave good results, 

 but to get thinner sections paraffin alone was used. The 

 sublimate material was generally stained in bulk with borax 

 carmine, the rest on the slide with hajmatoxylin. Sections 

 Avere made of all stages from the young gastrula up to the 

 ninth day after hatching, but the earlier embryonic stages 

 can be most satisfactorily studied in the living egg, which is 

 extraordinarily transparent. After about the sixth hour, 

 however, the structure becomes somewhat complicated, and 

 sections are therefore of great value in confirming and 

 amplifying the observations made on the living embryos and 

 young. 



For staining larvsc for mounting whole Mayer's carmalum 

 gave much the best results. 



III. Embryonic Develoi'Ment. 



The eggs of Sagitta arc about 2 mm. in diameter, and are 

 laid in the early morning, and develop iloating not far from 



