MUSEUM OF COMPAEATIVE ZOOLOGY. 165 



ance, especially of the latter, can be easily understood : the nucleus has 

 been shrunk by dehydration in the course of preservation. This shrink- 

 age was prevented in a measure at certain points where the strong 

 threads of the network were connected with it. It is important in this 

 connection to call attention to the fact, that in those cases where the 

 cells were unusually small the nucleus was most nearly regular in shape 

 (Fig. 66). No particular attention was paid to this point when study- 

 ing the living animal, but in the sketches made at the time I find that 

 the nucleus, which in general size and position agrees with this struc- 

 ture, was drawn with a regular oval outline (Fig. 2). This may well 

 . be its shape in life. 



The stalks of these four cells present a uniform appearance. They, 

 or at least their initial portions, stain more deeply than any other tissue 

 both in hsematoxylin and in carmine solutions, and hence are easily 

 traced so far as the stained portion extends. Under a high power the 

 stalk exhibits in places a faint longitudinal striation, and sometimes 

 shows lines of minute vacuoles between the striatious. The method of 

 termination in the cell has already been described. From the cells the 

 stalks pass directly into the brain, those of the first pair entering just 

 lateral to the second large ganglion cell on either side, and those of the 

 second pair just antero-lateral to the fifth pair of large ganglion cells iu 

 the brain (Plate V. Fig. 63, pd. cl. d.). The processes, which in trans- 

 verse sections appear to be directed toward the median plane, show in 

 longitudinal section (Plate VII. Fig. 2b, pd. cl. d.) a backward tendency 

 also. They may in this way be followed for a very few sections ; in the 

 last, in which they are prominent, one sees a splitting or branching of 

 the process in various directions, but beyond this the parts can be 

 traced at most a couple of sections. The more compact character of the 

 mass and the large number of other fibres make it difficult to say 

 whether any part of the process extends farther, or whether the whole 

 is split up at this point into fine- fibrillse. The place where the splitting 

 begins is surrounded by a considerable number of small ganglionic cells 

 (Plate VI. Figs. 78, 82). 



Biirger ('91, p. 639) describes two pairs of large ganglion cells and 

 two subordinate pairs in the brain. His description is not in all points 

 clear, and to judge from appearances the figures do not correspond to 

 his interpretation. Of the structures which he calls " giant cells," the 

 anterior pair is my third or commissural pair ; his posterior pair corre- 

 sponds to my fifth pair. Of his subordinate cells, the pair which lies 

 close to the commissure corresponds perhaps to my second pair, and 



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