ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 55 



The ventral nerve-chain is very speedily regenerated"; a fact which is 

 to be correlated with its superficial position in the posterior region of 

 Annelids. The regeneration does not proceed from any one point, but 

 occurs along the whole ventral surface by the proliferation of the ecto- 

 derm-cells. The proliferating cells are of two kinds — neuroglia-cells 

 and ganglion-cells. The ccelom arises from immigrating ectoderm-cells, 

 which the author regards as probably the primitive condition, the embry- 

 onic origin from two mesoblasts being probably a caenogenetic pheno- 

 menon. The primary mesoderm of Meyer, that is the mesoderm which 

 forms muscles and connective-tissue, also arises from ectoderm, in part 

 directly and in part from the " neuro-muscular primordia," whose origin 

 is obscure. The parapodia have a double origin, the chastse-sacs arise 

 from ectodermic invaginations, the cirri from the neuro-muscular 

 primordia. 



In general, in regeneration, while the ectoderm and endoderm retain 

 their characters as typical germ-layers, the mesoderm loses this charac- 

 ter and originates anew from the ectoderm. The great regenerative 

 activity of the ventral ectoderm in Polychaetes is to be associated with the 

 fact that its cells display little specialisation. These ventral cells are 

 arranged in bands, each of which has the power of regenerating special 

 structures, such as ventral nerve-cord, coelorn, lateral cirri, &c. In other 

 words, in each segment-cells occur with the power of regenerating the 

 organs of that segment. 



Regeneration in Earthworms.* — Annah Putnam Hazen has made 

 some interesting experiments. It has been shown by Spallanzani, Morgan, 

 and Hescheler, that a short piece cut from the anterior end of an earth- 

 worm dies without regenerating the posterior end, although such a piece 

 often lives for several weeks or even months. It was not known, however, 

 whether, if such pieces could be kept alive for a longer time, they would 

 regenerate, or whether, if regeneration did occur, a head or a tail would 

 develope. By grafting, in a reversed direction, the small anterior end of 

 one worm upon a large posterior piece of another worm, the small piece 

 can be kept alive for a much longer time. The results showed that a 

 head may regenerate from the posterior end of the seventh segment, if 

 it is kept alive for some months by grafting. It seems, comparing this 

 with other experiments, that the part of the body of the normal worm 

 from which the segments are taken determines what will be regenerated, 

 rather than the direction in which regeneration takes place. 



Phosphorescence in Earthworms.! — Prof. W. Blaxland Benham 

 notes that the large white earthworm (Octochxtus multiporus) of New 

 Zealand has a milk-coloured coelomic fluid of very great tenacity, which 

 can be drawn out in strands, and soon hardens on exposure to air. In 

 the dark, when the worm is handled, this fluid is discharged abundautly 

 from the dorsal pores and from' the mouth, which it reaches through 

 the " peptonephridia " opening into the buccal cavity. The fluid is 

 brilliantly phosphorescent when freshly discharged ; it contains numbers 

 of colourless " elaeocytes," and a remarkable kind of corpuscle contain- 

 ing a thread-like structure not unlike those described by Goodrich in 

 an Enchytraaid a few years ago. Benham suggests the need for a fresh 



* Anat. Anzeig., xvi. (1899) pp. 53G-41 (6 figs). f Nature, lx. (1899) p. 591. 



