1903.] NATURAL SCIENCES OF PHILADELPHIA. 379 



probable that it forms the secretion for the tube, since it is of very large 

 size in those large individuals with fully-formed tubes. 



Germarium, oviduct. — The germarium {Ov., figs. 9, 10) is a more or less 

 spherical organ placed on the ventral side of the body, composed of a 

 syncytium (fig. 17) containing fully fifteen large nuclei which are nurse 

 cells (yolk cells), and with at one end much smaller nuclei (ovogonia). 

 The whole is surrounded by a nucleated membrane which is continued 

 as a thin-walled unpaired oviduct (Ovd.) to open into the ventral sur- 

 face of the cloaca between the rectal and the nephridial openings. 

 One ovum matures at a time within the germarium, then is discharged 

 into the oviduct which serves as a uterus for its further development 

 until it reaches the free-swimming stage. As many as four or five 

 embryos are to be found at once in the uterus. 



Nervous system. — Most of the preceding writers have mistaken the 

 dorsal glandular body for the ganglion, while Vallentin recognized this 

 body as glandular, but supposed it to open by a duct into the alimentary 

 canal, and considered the large hypodermal cells at the bases of the 

 arms to be nerve cells. The cerebral ganglion (Cer-., figs. 9, 10) lies 

 directly below the dorsal glandular mass, is elongate from side to side 

 and approximately cylindrical on lateral view. On stained prepara- 

 tions I could determine that it is composed of many small nerve cells, 

 the nuclei of which stain deeply. On lateral view of the expanded 

 living animal (fig. 9) the following nerves are seen to arise from it : 

 (1) One pair which passes directly dorsad or dorso-caudad to innervate 

 the dorsal sense-organ (D.Sens.O.) ; this pair penetrates the dorsal 

 glandular body, and probably represents what Vallentin mistook for 

 a glandular duct leading into the vestibulum. (2) A pair of nerves to 

 each lateral sense-organ (L.Sens.O.). (3) An unpaired, very delicate 

 median nerve to the dorsal hypodermis behind the dorsal sense-organ. 

 (4) A pair of nerves which pass backward upon the sides of the prov- 

 cntriculus (Prov.). And (5) a pair of nerves, the largest of all, which 

 pass ventrad on the sides of the proventriculus. I have found no 

 evidence that the large hypodermal cells at the bases of the arms are 

 nervous; the long fibres which Vallentin found proceeding from them 

 probably represent the continuations of these cells to form the walls of 

 the arms. 



Sense-organs. — Eyes were seen only in one individual, a pair of small 

 red spots (E., fig. 9), lying close to the cerebral ganglion. The dorsal 

 sense-organ {D.Sens.O., figs. 9, 10) is a slight thickening of the hypo- 

 dermis bearing a tuft of short sense hairs, which penetrate a circular 

 aperture of the cuticula. Each lateral sense-organ (L.Sens.O.) has 



