Mr. F. S. Conant on the ChcBtognaths. 207 



here normally. In agreement with Hertwig, I have never 

 found spermatozoa in the ovary. Neither do the eggs appear 

 to be fertilized in the oviduct. Before they pass out of the 

 ovary a number of very small chromosomes (the exact number 

 was not determined) are found toward the inner end of the 

 ovum, or the place where the germinal vesicle disappears. 

 During the twenty to thirty minutes that the eggs are in the 

 oviduct before being laid there are no changes in these bodies, 

 and they continue to be the only chromatin that I am able to 

 find in the &gg until after the laying. The probability is, 

 therefore, that the spermatozoa come in contact with the eggs, 

 shortly before or during the process of laying, in the duct to 

 the exterior common to the oviduct and receptaculum seminis. 



Self-fertilization seems to be impossible, although the male 

 and female elements develop at the same time. In the case 

 of a 8. Mspida isolated when the ovaries contained only 

 immature ova, I found that by the second morning 30 or 40 

 eggs had matured and been laid, on the third 24 more, on the 

 fifth 68, on the seventh 55-58. Of these the only ones that 

 developed were fourteen out of the first lot, evidently fertilized 

 by spermatozoa remaining in the receptaculum seminis. In 

 all the others development proceeded only so far as the forma- 

 tion of the polar bodies. In this case the extrusion of the 

 polar bodies is evidently not dependent upon the entrance of 

 the spermatozoa, which Boveri states is necessary in the ova 

 of 8. hipunctata observed by him. 



The eggs when laid become attached to the sides of the 

 dish by a gelatinous or mucilaginous substance, which facili- 

 tates handling somewhat, but also collects dirt. The develop- 

 ment of the young 8agitice up to hatching is completed in 

 about thirty-six hours in warm weather. When hatched 

 they have practically the adult structure, and in four or five 

 days they are found to eat each other with as much zeal as is 

 shown by their elders in the same performance. It is inter- 

 esting to watch a Sagitta^ with a relatively narrow digestive 

 tract two thirds the length of its body, forcing down its 

 oesophagus a fellow of equal size, and hence one third longer 

 than the tract. The eating one another seems to be done 

 purely out of natural depravity, for it occurs when plenty of 

 the usual food, small tow-stuff, is present. 



Upon the development of the eggs I have nothing to add. 

 Like the previous observers, I have been unable to find a 

 satisfactory method of preservation, in spite of many trials. 



