1903.] NATURAL SCIENCES OF PHILADELPHIA. 373 



there may be a differentiation within the latter of a dorsal sensory and 

 a motor or sphlanchnic ventral portion. The nerve cells in the brain 

 are quite numerous and symmetrically arranged, but cell boundaries 

 are distinguishable only in the case of the two huge cells. Two con- 

 secutive sections of one and the same ganglion are figured (figs. 7, 8)> 

 cut in an obliquely horizontal plane, one passing through the nerves 

 to the lateral antennse and one of the huge cells (fig. 8), and the other 

 (fig. 7) passing further forward. In the latter can be seen what appears 

 to be a transverse fibrous commissure on the ventral surface of the 

 ganghon. The nerve cells are thus arranged mainly dorsally and 

 posteriorly. 



There are no recognizable nerve cells on the ventral surface of the 

 alimentary tract, as far as can be determined by the usual staining 

 methods. 



Sense-organs. — The dorsal sense-organ (D.Sens.O., figs. 2, 6) is a 

 specialization of the hypodermis on the dorso-midline of the corona? 

 and was discovered by Gast. It consists of a group of cells (fig. 6) in 

 which one large and five small nuclei can be seen, which compose a 

 thickened area of the hypodermis, and above which there is a small 

 annular thickening of the cuticula; no sense hairs were seen. The 

 antero-lateral sense-organs, also discovered by Gast, lie each (A.Sens.O., 

 figs. 1, 6) upon the side of the corona, as a thickening of its wall. Each 

 consists of a cytoplasmic mass containing four large nuclei immediately 

 imbedded in a more granular cytoplasm, while into a more hyaline 

 cytoplasm extends a slender cylindrical rod from the cuticula; there 

 are thus some differences from the relations in lentiformis. A single 

 nerve, containing a nucleus at its junction with the cerebral ganghon, 

 innervates each of these organs. The postero-lateral sense-organs 

 (lateral antennse) lie each on the side of the corona somewhat ventral 

 near the junction of the trunk (L.Sens.O., figs. 1-3). To each passes 

 one large nerve, with a large nucleus at its peripheral end ; and as Gast 

 also observed, the organ itself consists of a tubercular elevation of 

 the body wall, and on the apex of this a cylindrical cuticular process, 

 bearing a tuft of long, non-vibratile sense hairs (fig. 6) ; the base of the 

 cuticular process is enlarged and extends below the hypodermis. 



Body cavity, connective tissiies. — The body cavity contains a clear 

 fluid in which float masses, varying in number and size, of a brown 

 color; these are non-cellular and probabh' represent bA'c-products of 

 metabolism. The connective tissue elements are branched, naked 

 cells with many processes, constantly changing their form and moving 

 about through the body cavity. They are frequently found in close 



