ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 593 



Peculiar Abnormality in Proboscis of a Nemertean.* — M. Caullery 

 describes the occurrence in Tetrastemma candidum of a double proboscis. 

 Within the same sheath they lie end to end in opposite directions, with 

 the armatures turned toward the two ends of the animal. 



Histogenesis of Cysticercus pisiformis.t — R. T. Young finds that 

 this bladder-worm shows an extremely simple type of histogenesis, tbe 

 various tissues being developed exclusively by modification in situ of 

 a pre-existent undifferentiated parenchyma. In correspondence with its 

 simplicity of development, Timia serrata shows a very simple type of 

 adult structure, the various tissues being comparatively little differen- 

 tiated from one another. , 



It is very doubtful where there is any ectoderm or any process of 

 gastrulation. The lack of a true epithelium and the simple character of 

 its tissues and mode of nuclear increase are probably expressions of the 

 degenerate character of this tapeworm. 



" The role of the chromosomes in heredity is entirely lost ; the nucleus 

 is probably not a morphological, but a physiological unit ; the fate of 

 any cell is determined not by its morphological structure, but rather by 

 its physiological environment." These are generalisations, but the 

 paper gives a detailed account of the process of development. 



Incertse Sedis. 



Larva of Pedicellina Echinata.| — R. Czwiklitzer describes this 

 interesting larva and shows how it may be interpreted as a modified 

 Trochophore. He compares the Ectoproct and the Endoproct larva in 

 detail, and shows the affinities between them in structure and in mode 

 of fixation. It may be that the Phylactoltemata are derived from the 

 Phoronidte (them ganglion being, in that case, supra-cesophageal), and 

 the Gymnolaemata from the Entoprocta (their ganglion being, in that 

 case, sub-cesophageal). 



Spermatozoa of Fresh- water Bryozoa.§ — F. Braem describes the 

 spermatozoa of Plumatella, Pectinatella, and Fredericella (three related 

 Phylactolamiata), and shows that they differ markedly from those of 

 Paludicella (a typical representative of the Gymnolaemata). It is 

 interesting to find that the structural differences of the adult 

 organisms have their counterpart in the spermatozoa. 



Polyspermy in Membranipora.|| — Kristine Bonnevie finds that 

 polyspermy occurs regularly in this Polyzoon. There is a coalescence 

 of spermatozoa in groups in the spermatogenesis, so that a "sperm- 

 zeugma" results. One spermatozoon only seems to form the male 

 pronucleus, but the others may be useful in furnishing the necessary 

 chromatin (and chromidial apparatus) to re-establish the disturbed 

 nucleo-cytoplasmic relation in the ovum. 



* C.B, Soc. Biol. Paris, lxiv. (1908) pp. 738-40 (3 figs.). 



t Zool. Jahrb., xxvi. (1908) pp. 183-254 (4 pis.). 



j Arbeit. Zool. Inst. Univ. Wien, xvii. (190S) pp. 157-86 (1 pi. and 2 figs.). 



§ Zool. Anzeig., xxxii. (1908) pp. 671-3 (2 figs.). 



|| Jen. Zeitschr. Naturw., xlii. (1907) pp. 567-98 (4 pis.). 



Oct. 21st, 1908 -2 B 



