1901.] NATURAL SCIENCES OF PHILADELPHIA. 727 



ova that accompany the Gregarines. " The "ova" measured 

 about 5^(j inch in diameter and each contained an "embryo" 

 that made evident movements. They have two coats, an inner 

 faintly striated and an external without markings. The con- 

 tained " embryo " is finely granuhxr and has a large pale nucleus. 

 M' Intosh regards these ' ' ova ' ' as altogether diSerent from the 

 true ova of the Borlasia. 



Wheeler found in the body cavity of the Annelid Myzostoma 

 glabrum great numbers of amoeboid masses that he regards as pos- 

 sibly the young stages of some Gregarine. The body cavity was 

 distended with ova, and among them occurred the parasites. He 

 says: " In most cases the uniformly staining and rather shrunken 

 body of the parasite was produced into a long fine point which 

 had penetrated the cytoplasm of an ovum. In a few instances a 

 single amoeba had two points, each entering the body of an adja- 

 cent ovum (fig. 54). ' The cytoplasm of the ova thus attached 

 contained large granules which took up the hsematoxylin with 

 avidity. These granules were larger and more numerous than 

 those which occur in normal ova of about the same size." The 

 amoebae are also found outside the ova. 



IV. General Conclusions. 



The description of the organs of Zygeupolia given in the ana- 

 tomical section of this paper makes it evident that this genus is a 

 primitive one and that it has affinities with both Proto- and Hetero- 

 nemerteans. 



The questions now to be discussed are (1) the relationship of 

 Zygeupolia to other orders, especially the Protonemerteans ; 

 (2) the position of Zygeupolia within its own order. 



The following characters undoubtedly entitle Zygeupolia to a 

 place in the order of the Heteronemerteans: the position of the 

 lateral nerves, outside the circular muscle layer; the presence of 

 the cutis and outer longitudinal muscle layer ; the situation of the 

 mouth behind the brain; the absence of stilets in the proboscis 

 and of a blind intestine. 



The alimentary system of Zygeupolia conforms with the general 

 Heteronemertean plan, which, however, is essentially the same as 

 that of the Mesonemerteans and such Protonemerteans as Cari- 

 nina and Hubrechtia. 



