354 L. DONGASTEK. 



II. Material and Methods. 



Tlie material lor my work was obtained partly at Naples 

 and partly iu tlie " Pantauo " at Faro, near Messiua. The 

 Pantano is a lagoon about half a mile in diameter, con- 

 nected with the Straits of Messina by a shallow canal. In 

 summer, when the water is exceedingly warm, one species of 

 Sagitta is very abundant, and during the first two weeks of 

 July, 1900, I obtained a number of eggs in all stages of 

 development by fishing with the tow-net at a depth of fifteen 

 to twenty feet. After allowing the '^ Auftrieb " to settle for 

 a short time, the bottom layer was drawn off with a syphon 

 and searched with a lens, and in this way quantities of eggs 

 could generally be obtained. I have not been able to deter- 

 mine this species of Sagitta with absolute certainty; the 

 adults were generally found at a considerably greater depth 

 than the eggs, although the young occurred at all depths ; but 

 as only one species was found, there can be little doubt that 

 the eggs belonged to it. The adult Sagitta belonged in all 

 probability to the species bipunctata, although it does not 

 entirely agree with Grassi's description ; but I have found that 

 this species is very variable, and am inclined to believe that 

 possibly two species have been included under the name 

 " bipunctata.'^ 



The eggs obtained at Faro developed very rapidly. At 7 

 a.m. gastrula) were found, and the young Sagitta generally 

 hatched between 6 and 8 p.m. the same evening. The eggs 

 were therefore preserved at intervals during the day in order 

 to get a complete series of the embryonic development. The 

 methods of preservation adopted were (a) with sublimate con- 

 taining 20 per cent, of acetic acid, and {h) with osmic acid for 

 a few minutes followed by MiUler's solution for several hours. 

 Of these methods, the first gave good results ; the second was 

 fairly good for the young after hatching, but the embryos in 

 the shell treated in this way wei-e rarely satisfactory, beinti; 

 very brittle and niucli contracted. Possibly the osmic acid 



