Messrs. Hancock and Embleton on the Anatomy of Eolis. 189 



them, and the commissures, excepting the modifications to be 

 presently mentioned, are pretty much the same, as far as we have 

 been able to examine them, as they exist in E. papillosa. 



In E. coronata the olfactory tractus are much shorter, and 

 their ganglia more globular, and of much greater relative size 

 than in E. papillosa, being indeed more than one-third the size 

 of the lateral supra-cesophageal ganglia themselves. There is 

 besides one principal nervous stem from the ganglion which runs 

 up the central axis of the tentacle. 



In E. Drummondi the relative size of these ganglia is still 

 greater and their form elliptical. The existence of these ganglia 

 we believe to be constant in all the species ; we observed them in 

 E. pellucida, E. Farrani, E. alba, E. gracilis^ E. picta, E. punc- 

 tata , &c. 



The three nervous collars of the oesophagus can be observed 

 easily in E. Drummondi, in which there appears to exist at the 

 coming off of the genital nerve from the middle or slender collar 

 a small ganglionic swelling 6. A similar swelling occurs also in 

 E. coronata. 



When viewed attentively with the naked eye, the cerebral 

 ganglia, and particularly the first or median pair, present a num- 

 ber of large globular vesicles inclosed within a transparent mem- 

 branous envelope. When compressed and somewhat magnified, 

 all the ganglia seem to be made up of masses of vesicles, as the 

 view of a buccal ganglion, PI. VI. fig. 3, will show. Under a 

 higher power these vesicles or cells are found of very variable 

 size, externally smooth, internally granular, and having one or 

 more large distinct nuclei and nucleoli ; some have only one large 

 nucleus and a distinct nucleolus ; the interior is filled with smaller 

 cells of different dimensions and also nucleated ; the smallest of 

 all however are minute, clear, bright cells, probably nuclei or 

 rather nucleoli of larger vesicles. Many of these last are found 

 also lying in the intervals of the large cells intermixed with the 

 tenacious semifluid matrix that imbeds the nervous vesiclfcs, and 

 in which no distinct forms can be discerned. On tearing up one 

 of the cerebral ganglia and examining the contents of the mem- 

 branous envelope in the compressor, under a high power (one- 

 eighth object-glass), numbers of the cells of all sizes are seen 

 under the form of pear-shaped, largely nucleated vesicles, PL VI. 

 fig. 4, having a long pedicle attached ; the nucleus, which is very 

 large, has an evident and well-marked nucleolus, and the pedicle 

 or stalk of the cell is in the interior very finely granular. Groups 

 of these pedicled ovoid vesicles may be observed, such as that at 

 PI. VI. fig. 3, their pedicles all lying in the same direction, and 

 tending either to unite or to run on parallel to each other, put- 

 ting us strongly in mind of some of the simpler forms of glan- 



