MUSEUM OF COMPARATIVE ZOOLOGY. 175 



female.^ Furthermore, in the entire collection which Professor Verrill 

 kindly placed at my disposal there was only one female, that one being 

 found coiled up in a mass of twenty specimens. 



Biirger (p, 647) describes one form which differs materially in struc- 

 ture from all others studied by him ; he was inclined to regard it as a 

 female. He found a sac with flattened walls hanging from the dorsal 

 line. The description and figures given by him resemble strongly an 

 immature testis, — certainly it cannot be an empty ovary. But the ter- 

 mination which he describes for it is so extraordinary that one must 

 doubt the normal nature of the specimen or the accuracy of the obser- 

 vations. Certainly neither in male nor female does one find anything 

 like the tube and cells which he describes as lying on the ventral cord, 

 except the oesophagus. It is impossible, however, that he has mistaken 

 the anterior for the posterior end of the worm, because he mentions the 

 head of this specimen. There are certain points in his description of 

 this individual, especially the lack of an anal ganglion, which recall the 

 female, yet in view of the many problematic points which cannot be 

 referred to either sex, I am of the opinion that this must have been a 

 very abnormal specimen. I shall give a description of the sexual organs 

 of the female without any further reference to his work, describing only 

 those conditions which I believe to be normal. 



The three females obtained present three stages in the growth of the 

 egg, but unfortunately all are too far advanced to give any clue as to 

 the place or method of origin of the egg cells. In the first stage the 

 body cavity is already half filled with well developed eggs, and no trace 

 of ovaries or of the walls confining the ova is present, but the ova 

 seem to lie free in the body cavity. Each egg (Plate IV. Fig. 60) has 

 a fi.rm outer membrane, highly granular protoplasmic contents, and a 

 large irregular nucleus, which has a very thin nuclear membrane and 

 is strikingly poor in chromatic substance. Between and around the eggs 

 one finds a granular substance, and more rarely small nuclei. 



In the next older stage the body cavity is more nearly filled, and the 

 eggs are very similar except that the nucleus is smaller and more deeply 

 stained. One finds also around each egg an external covering of minute 

 quadratic blocks, which seem to be easily separable from the egg and 

 from one another. 



The oldest stage observed differs from that just described in some 



1 I should not neglect to mention that a female with protruding egg mass 

 (see Fig. 10) would correspond generally to this description; but such a state 

 would hardly be available for identification. 



