654 SUMMARY OF CURRENT RESEARCHES RELATING TO 



In short, as age increases there is a diminution of the hermaphro- 

 ditism, and a predominance of maleness. Perhaps in course of time 

 Cucumaria laevigata will hecome dioecious. 



Red Pigment of Asterias rubens.* — E. Dubois finds that macera- 

 tion of this starfish in fresh water yields a fine blood-red liquid. This 

 does not contain haemoglobin, nor does it fix the atmospheric oxygen. 

 Addition of ether produces a change of colour to strong yellow ;md 

 separates an albumin. The pigment is ferruginous, but does not show 

 the characteristic spectrum. 



Natural Parthenogenetic Development^ — C. Viguier reasserts 

 his conviction that parthenogenetic development may occur naturally in 

 sea-urchins — Spheerecliinus, Toxopneustes, and Arbaeia. He has obtained 

 parthenogenetic plutei from Toxopneustes, and gastrulae from Arbaeia ; 

 and he emphasises the fact that the parthenogenetic development differs 

 in some details from that which follows fertilisation. He also gives the 

 results of experiments which show that temperature has its influence on 

 the alleged natural parthenogenetic development. 



Maturation in Echinus esculentus.^ — T. H. Bryce has made an 

 important contribution to our knowledge of this process, and some of 

 his results help to harmonise the discrepancies of other accounts. His 

 comparison of his results with those of other observers is very interest- 

 ing, but we must confine ourselves to the summary of observations. 



The chromatin thread or threads, derived only from a portion of the 

 mass of chromatin in the germinal vesicle, are found split longitudinally 

 and segmented into sixteen bodies — half the number of the chromatin 

 rods in the nuclei of the cleavage divisions. These bodies consist of 

 two short rods placed side by side, and each rod is composed of two 

 spheres united by a less deeply stained portion of the thread. The two 

 rods are intimately associated so as to form a tetrad-like mass, and the 

 whole figure is to be considered as a compound chromosome. 



After a relatively long prophase each of these is resolved in the first 

 polar metaphase in such a manner that while the body is opened up 

 along the original cleavage plane, another longitudinal cleft is effected, 

 which is completed in the anaphase, and the final result is another com- 

 pound chromosome like the original from which it sprang except in size. 

 Each of the sixteen double rods which remain in the ovum after the 

 extrusion of the first polar body is resolved in the second polar spindle 

 into its two elements without further cleavage taking place. 



In the telophase of the second division the elements which remain 

 in the ovum after the extrusion of the second polar body elongate into 

 rods which become bent on themselves, while those in the second polar 

 body remain condensed as small bilobed rods. 



The maturation phases differ from the ordinary cleavage mitoses in 

 respect of (a) the thickening and condensation of the chromatin rods, 

 (b) the second longitudinal splitting which occurs in the first meta- 

 kinesis, and (c) the absence of longitudinal cleavage in the second meta- 

 kinesis. The second mitosis thus merely distributes the grand-daughter 



* Ann. Soc. Lyon, xlvii. (1901) pp. 139-41. 

 f Coiuptes Keudus, exxxv. (1902) pp. 00-2. 

 X Quart. Jouru. Micr. Sci., xlvi. (1902) pp. 177-224 (3 pis. and 3 figs.). 





