Journal of Applied Microscopy. 



219 



obtainable material for investigating 

 such nucleated red blood cells were anae- 

 mic blood, bone marrow, and blood of 

 vertebrate embryos. It was deemed wise 

 to include in this study the blood of some 

 of the lower animals in order to bring 

 embryonic conditions into their true 

 relations. Amphibian blood was chosen 

 for this purpose and observations carried 

 out on uncolored preparations, especially 

 to clearly recognize the artificial products 

 caused by staining processes. 



In some megaloblasts the nuclei ap- 

 pear as completely structureless white 

 drops, and are called red ematous nuclei; 

 they are not artefacts since they can be 

 found in quickly made, thoroughly dried 

 coverglass preparations; also if the blood 

 is fixed in sublimate as it is shed. The 

 best fixer of hemaglobin and nuclear sub- 

 stance, in amphibian blood at least, was 

 shown to be a mixture of concentrated 

 sublimate and freshly prepared two per 

 cent, osmic acid in equal parts. After 

 treatment in alcohol and ether and flam- 

 ing, the preparations were dried in a 

 dryer and held for a moment over an am- 

 monia flask; then washed in the fixing 

 fluid, and flnally in very weak pyrogallic 

 acid, and last in distilled water. 



Colored preparations were made from 

 fresh unfixed blood, and after the fixing 

 of dried blood. The following colors were 

 finally used: Erlich's triple glycerine 

 mixture (containing Aurantia, Eosin), 

 Spuler's orange-eosin, aurantia-S. fuch- 

 sin. corallin benzo-purpurin, aurantia- 

 methyl orange, congo red. Several dif- 

 ferent neutral mixtures were tried, 

 Erlich's triacid and the gold-orange or 

 bergonzini. This mixture acted so that 

 the red alone was only present as a trace 

 compared with the orange. Many inter- 

 esting features were made out in tissues 

 examined, but the methods are of great- 

 est mterest. A. M. C. 



licwis, Margaret. Studies on the Central and 

 Peripheral Nervous System of the Polychaete 

 Annelida. Proc. Am. Acad. Arts and Sci., 33: 

 No. 14. 



A paper with eight plates by Margaret 

 Lewis gives the results of her investiga- 

 tions upon the nervous systems of Cly- 

 mene pro lucta, and Axiothea torgnata. 



Aside from the general morphology of 

 these Maldanid worms, she has paid 

 special attention to Leydig's fibers, the 

 centrosome of the ganglion cell, and the 

 sense organs. 



The term "Leydig's fiber" is used to 

 designate the annelidan structure known 

 under the different names of Neurochord, 

 giant fiber, central canal, and neural 

 canal. 



She finds confirmation of the views that 

 Leydig's fibers in annelids are true nerve 

 fibers; that the sheath of these fibers is 

 comparable to the medullary sheath of 



nerve fibers in vertebrates; that the con- 

 tents are comparable to the axis cylinder; 

 and hence, that the distinction made 

 between the nerve fibers of vertebrates 

 and invertebrates cannot be maintained. 



In the Maldanidae these fibers do not 

 function in any way as an organ of sup- 

 port. They are neither homologous nor 

 analogous to the chorda dorsalis of ver- 

 tebrates. 



They result- from the union of direct 

 processes of giant ganglion cells. In the 

 forms studied these cells appear in the 

 sub-oesophageal ganglion and are found 

 scattered along the lateral and ventral 

 portions of the ventral nerve cord with- 

 out indicating metamerism or symmetry. 

 In the sub-oesophageal ganglion, how- 

 ever, they show an approach to 

 symmetry. 



The substance of the Leydig's fiber is 

 uniform throughout, and does not repre- 

 sent a bundle of nerve fibrillae; further, 

 the fiber does not show any indication of 

 being a degenerate structure. The rela- 

 tion of the process of one giant cell with 

 that of another appears to be one of 

 direct continuity, not of simple conti- 

 guity. If Leydig's fibers are true nerve 

 fibers, as maintained, they stand in their 

 relation to ganglionic cells, in strong 

 opposition to the neuron theory of Wald- 

 eyer, Edinger, von Lenhossek, and others. 

 The giant cells giving rise to these fibers 

 possess a nucleus which is always eccen- 

 tric in position, and a centrosome and 

 sphere which are more central in 

 position. 



The division of nerve cells was 

 observed in these worms and the pres- 

 ence of the centrosome is taken as an 

 argument that it has some function other 

 than that of cell division. 



A note in this connection by E. L. Mark 

 calls attention to the importance of the 

 question whether a genetic connection 

 may be established between the so- 

 called centrosome which exists during 

 cell division. 



The centrosome in these ganglion cells 

 is evidently a center of mechanical activ- 

 ity, as shown by the eccentric position cf 

 the nucleus, the frequently observed 

 flattening of the nuclear membrane on 

 the side toward the centrosome, the con- 

 centric arrangement of the protoplasm 

 around it and by the radiations extending 

 out from it. 



The presence of a centrosome in gang- 

 lionic cells is an argument for its being 

 a permanent cell organ. Some of the 

 giant cells show two centrosomes and 

 spheres without any evidence of 

 approaching nuclear division. 



Parts of the peripheral nervous system 

 of both worms terminate in multicellular 

 sense organs, occurring abundantly 

 throughout the integument in certain 



