390 MONTGOMERY. [Vol. XIII. 



compels us to refer briefly to the methods of fixation with 

 which this investigator's material had been preserved. Part of 

 it was fixed with weak chromic acid solutions, which are not to 

 be recommended. He states, further, that "Die Behandlung 

 derjenigen \Cerebratulus marginaius, Langia] aus der Zoolo- 

 gischen Station in Neapel ist mir unbekannt"; the fixative 

 used for these, I presume, had been sublimate in alcoholic 

 solution — a method much employed at the Naples laboratory. 

 Thus Burger had used neither Hermann's nor Flemming's 

 fixation fluids, both of which demonstrate the fine-grained 

 structure of the peripheral spongioplasmic layer much more 

 clearly than does sublimate, which generally produces a fusion 

 of the microsomes into larger granules.^ A similar fine-grained 

 layer of spongioplasm may almost always be found enveloping 

 the nucleus. 



As has been already remarked, the greater part of the cyto- 

 plasm is coarsely vacuolar, in that staining, non-fibrillar, spongio- 

 plasmic meshes envelop various-sized, unstaining, structureless 

 vacuoles of hyaloplasm, which in life is probably fluid. There 

 does not seem to be any concentric or other regular arrange- 

 ment of these vacuoles around the nucleus, though Burger has 

 given two figures exhibiting such a distribution ('30b, Fig. 6i d, 

 '91b, Fig. i8 «, the latter from life); this author considers that 

 such an arrangement of the hyaloplasmic vacuoles is the natu- 

 ral one, and that preparations which show no such arrangement 

 are artifacts. Now while I have never observed any such 

 regular arrangement, I would not maintain that it does not occur, 

 but merely that it must be very infrequent; but, on the other 

 hand, the irregular grouping of vacuoles of unequal size must 

 not be regarded as artificial, but as normal, since it is found 

 after the use of the most diverse fixing reagents. I consider 



1 This peripheral, fine-grained layer of the cell had been seen by Leydig ('64), 

 who quite correctly showed that it does not correspond to a cell membrane. But 

 H. Schultze ('79), who found it to be continued along the axis cylinder, considered 

 it a true cell membrane. Nansen ('87), as I understand him, was unable to decide 

 whether the ganglion cells possess true membranes or only such as are formed by 

 the encircling neuroglia fibres. Rohde ('90a, '92) supposed all the spongioplasm 

 of the ganglion cells of Polychaeta and Hirudinea to be fibrillar, and composed of 

 neuroglia fibres which had penetrated the cell. 



