682 PROCEEDINGS OF THE ACADEMY OF [DeC, 



the first type in Zijfjeupolia, figs. 20, 9, G.C.u which are found 

 abundautly on tlae dorsal and outer lateral sides of the dorsal 

 lobes, and on the outer lateral sides of the ventral lobes. They 

 are very numerous around and in the cerebral organs. 



The cells of the second type, figs. 20, 10, G.C.n, are elongated 

 and pear-shaped. The cytoplasm is more abundant than in I, 

 the nucleus is oval and centrally placed, containing relatively less 

 chromatin than that of I. These cells are arranged usually in 

 radiate clusters, and their distribution in Zygeupolia agrees with 

 that described for other Nemerteans by Biirger and Montgomery, 

 namely, on the ventral lobes and along the lateral chords, never 

 in the dorsal lobes. 



The cells of the third type, figs. 20, 8, G. C. i„, are much larger 

 than either I or II, but vary considerably in size. They are 

 long, pear-shaped cells, with the greatest diameter proximally. 

 The nucleus is lai'ge, round, and centrally placed, with a large 

 nucleolus, and the chromatin distributed throughout the nucleus. 

 Montgomery states that " while the cell bodies vary considerably 

 in size, their nuclei remain of nearly uniform dimensions." 

 These cells are found in both dorsal and ventral lobes and along 

 the lateral chords. 



A fourth type of cell has l)eeu discovered and named by Burger 

 (1894), namely, the colossal neurochorcl cells. Burger (1899), 

 p. 105, states: " Neurochordzellen fand ieh bei alien von mir uuter- 

 suchteu Cerebratuleu, ferner bei Lanrjia formosa. Das Gehirn 

 besitzt stets nur ein eiuziges Paar von Neurochordzellen, welches 

 an der medialen Fliiche der ventralen Ganglien dort gelagert ist, 

 wo die Schlundnerven entspringen. Zahlreiche Neurochordzellen 

 befindeu sich indessen im GanglienzellbelagderSeitenstiimme . , , ." 

 Biirger also found in the Metanemerteans Drepanopliorus and 

 Prosadenoporus one pair of neurochord cells in the braiu, but 

 none along the lateral chords. The presence of neurochord cells 

 in Cerebratalus lactem has been demonstrated by jNIoutgomery 

 (1897 6), who found that " the colossal ganglion cells (IV) of 

 Cerebndidas are present in three pairs in the ventral brain lobes, 

 and are distributed irregularly along the lateral chords, but are 

 wholly absent in both ends of the latter (namely, in the oesopha- 

 geal region and in the caudicle)." 



In ZijgeupoUa a pair of large cells is found on the median sides 



