690 PROCEEDINGS OF THE ACADEMY OF [Oct., 



in annelid larvae (protoncphriclia). Careful study of fixed and living 

 material has thus far afforded me no CA'idcnce whatever of nephridia 

 of any sort. 



The ova which were studied in the preparation of this paper were 

 collected from the sea-water aquaria in the vivarium of the University 

 of Pennsylvania during the months of January to May, 1902. 



The ova arc laid in gelatinous capsules as described by Korschelt for 

 D. apatris, each capsule containing three to seven ova of two sizes, the 

 smaller about one-third the diameter of the larger. The smaller ova 

 give rise to the minute and degenerate males, while the larger ova 

 give rise to the female individuals. The number of the large female 

 ova exceeds that of the male. In fifty capsules 214 ova were counted, 

 of which number 79 were male ova and 135 female. These latter have 

 been the object of my investigation, the small size (ca. 30 micra in 

 diameter) and smaller number of the male ova rendering them much 

 less favorable for study. The capsules were found attached to the 

 various sea-weeds in the aquaria, and particularly to the Ulva. A 

 quantity of the sea-weed was taken from the tanks in which the animals 

 were found to be most abundant and squeezed over a large watch 

 crystal. The eggs thus washed out from their capsules, together with 

 much vegetable debris, soon settled to the bottom of the watch crystal, 

 from which they were picked out, under a lens, by means of a fine- 

 pointed pipette and transferred to a small vessel. The vessel found 

 most useful for this purpose was made from the hemispherical bottom 

 of a small test-tube cemented to a slide. The ova collected in this 

 manner proved to be in all stages of development, from the unseg- 

 mented ovum to an embryo ready to escape. 



The ova were in all cases killed Avith Ivleinenberg's stronger picro- 

 sulphuric fluid, and after washing in 70 per cent, alcohol, were stained 

 with Conklin's (1902) picrohsematoxylin. This method of fixing and 

 staining has proved satisfactory with so many forms that it was con- 

 sidered advisable, in view of the scarcity of the material, not to experi- 

 ment further. The ova were then dehydrated, cleared in cedar oil 

 or xylol, and mounted in balsam under covers supported by thin glass 

 feet, thus providing a space in which the eggs may be rolled about by 

 displacing the cover glass. 



It has been noted by several observers that Dijwphilus practically 

 disappears at the approach of warm weather, and this fact was found 

 to be true in this case also. This is interpreted by Korschelt to mean 

 simply that the period of sexual activity has come to an end. How- 

 ever, species of Dinophilus have been found at Wood's Hole, Massachu- 



