No. 3.] STUDIES ON THE HETERONEMERTINI. 385 



elusions that the nemertean ganglion cell is multipolar must 

 either have been based upon the study of poor preparations or 

 have been the result of preconceived views. 



A. Cell I. 



In Lineus gesserensis these smallest ganglion cells are 

 usually densely massed together and of a shortened pyriform 

 shape (Fig. i). The nucleus is very large in proportion to the 

 cell body, in fact nearly filling it; it is relatively very much 

 larger, but varies less in size, than those of the other ganglion 

 cells.^ The nuclei vary from a spherical to an elongate-oval 

 shape. Their chromatin is not limited to the periphery, but 

 distributed in the form of nearly equally sized grains (of the 

 number of ten or more in each nucleus), placed throughout the 

 faintly staining nuclear sap; I have been unable to constate an 

 achromatic network. In the nucleus one or two nucleoli may 

 sometimes be found ; these stain deeply with eosin, are of a 

 spherical shape, and are larger than the chromatin masses. 

 Sometimes an elongated "tail " of the nucleus penetrates for a 

 short distance into the nerve tubule; but in none of the types 

 of ganglion cells have I seen such branches of the nucleus as 

 H. Schultze ('79) has described; it is to be noted that Leydig 

 also never saw such structures. The cytoplasm usually stains 

 very faintly, which is due to the excess of the hyaloplasmic 

 vacuoles, these being enveloped by only a fine spongioplasmic 

 meshwork.^ 



1 Biirger has shown conclusively that these are sensory and not motor cells ; 

 and it would be interesting, in view of the relatively great size of their nuclei, to 

 determine whether in other animal groups also the nucleus of the sensory is rela- 

 tively greater than that of the motor cell; in other words, whether the size of the 

 nucleus stands in relation to the function (sense, motion) of the ganglion cell. 



2 I shall employ in my descriptions of the cytoplasm the terms " hyaloplasm " 

 and " spongioplasm " to denote respectively the homogeneous, unstaining, and the 

 more or less granular staining constituents. Since Flemming ('82a) has by no 

 means proved the fibrillar structure of protoplasm, I see no reason to adopt, as 

 Rohde ('87) and Burger ('90b) have done, his terms "paramitom" and "mitom." 

 In a more recent paper ('92) Rohde has adopted Leydig's terms. The terms of 

 Leydig, "hyaloplasm " and "spongioplasm," are more widely applicable, and thus 

 preferable, since they express respectively the more fluid, homogeneous, and the 

 more dense, more compound portions of the cytoplasm. I have never found a 



