ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 66 



main median portion is the seat of lymphocyte formation, and the con- 

 nection with the oral blood-ring is similar ; (b) the upper lateral 

 appendix probably forms no lymph-cells, but, as it contains muscular 

 elements, has probably some contractile capacity ; (c) the lower distal 

 portion is an excretory vesicle. 



2. The median lymph-forming portion is united to the oral vascular 

 plexus in the annular septum by the connecting portion already men- 

 tioned ; the axial sinus opens into the internal oral perihasmal canal. 



3. There are muscle-fibres in the annular and in the radial septum. 



4. The blood-spaces in the rays occur especially in the transverse 

 bands and lateral "Kolbchen," from which blood channels pass to the 

 tube-feet, forming an annular sinus at their ends. 



Parthenogenesis in Sea-Urchin Ova.* — C. Viguier re-states his 

 conclusion that in the course of one season the eggs of the sea-urchin 

 pass through a succession of stages : (1) even when apparently ripe they 

 may after fertilisation produce ova whose development is soon arrested ; 

 (2) when fertilised they form perfect larvae, when not fertilised they do 

 not develop ; (3) when fertilised they form perfect larvae, but they may 

 also produce parthenogenetically less advanced larvae ; (4) they may 

 develop much in the same way whether fertilised or not ; (5) the fer- 

 tilised ova are arrested or lag behind the parthenogenetic ova. 



Hybridisation of Sea-Urchin and Comatula.f — E. Godlewski jun. 

 states that he has succeeded in rearing plutei from Echinus-ova, fertilised 

 by Antedon -spermatozoa when the sea-water is altered in its alkalinity 

 by adding some solution of sodium hydrate. In spite of the nuclear 

 union there is in the larva no hint of paternal characteristics. Fer- 

 tilisation and mingling of hereditary characters are two quite distinct 

 processes. It seems to the author unjustifiable to regard the chromatin- 

 substance as the sole vehicle of the hereditary qualities. The experi- 

 ments show that the ovum-cytoplasm must count for much. 



Muscles of Fsdicellariaa.l — E. Kiernik has found in Paracentrotus 

 and Par echinus (as Hamann did in Echinus acutus) six neuroderm 

 organs, two for each blade. In the adductor muscles there are true 

 striped muscles along with smooth muscles. The extensors and flexors 

 consist entirely of smooth muscle fibres. 



Antarctic Holothurians.§ — Remy Perrier reports on the collection 

 in the Museum of Natural History in Paris, and discusses the question 

 of bipolarity. His view is that we cannot speak of a bipolar fauna, 

 though there are bipolar species, whose distribution must be separately 

 interpreted in each case. In most cases the bipolar species are the relics 

 of very widely distributed species, whose inter-tropical representatives 

 have been eliminated by the keen struggle in tropical regions or by 

 relatively recent climatic changes. 



* Arch. Zool. Exper., iii. (1905) Notes et Revue, pp. ccvii.-ccxii. 



t Bull. Internat. Acad. Sci. Cracovie, 1905, pp. 501-6. 



X Tom. cit., pp. 520-32 (1 pi.). 



§ Ann. Sci. Nat. Zool., ser. 9, i. (1905) pp. 83-146 (5 pis. and figs.). 



Feb. 21st, 1906 r> 



