ZOOLOGY A.N1) BOTANY, MICROSCOPY, ETC. 363 



Dipleuchlanis, a new Sub-genus for Euchlanis (Diplois) propa- 

 tula Gosse.* — P. de Beauchamp having found in material collected in 

 Syria, by H. G. de Kerville, a specimen of this aberrant Rotifer, pro- 

 poses to place it in this new sub-genus. 



Echinoderma. 



Extra-ovate Experiments on Sea-urchin Ova.f— Naohide Vatsu 

 obtained extra-ovates in Arbacia and Strongylocentrotus, by treating the 

 fertilized ova with diluted sea-water and then replacing them. An 

 extra-ovate was extruded at the height of turgor, the cleavage of the 

 egg was more or less abnormal. The abnormality is not due to the 

 diluted sea-water, as is shown by the fact that under the same treatment 

 all other eggs (without an extra-ovate) in the same vessel cleaved 

 normally, and by the fact that the disturbance in cleavage is found at 

 the spot where the extraovate is situated. The disturbance is due to the 

 deprivation of a portion of the cytoplasm as an extra-ovate. Thus we 

 may say that the cleavage pattern is already established in the fertilized 

 egg of Arbacia and Strongylocentrotus, as Driesch has shown in Echinus. 

 It may be noted that an egg with an extra-ovate gives rise to a perfect 

 pluteus. 



Echinoderm Hybridization.! — D. H. Tennent has made numerous 

 experiments in Echinoderm hybridization, and gives a careful discussion 

 of the problems involved. The Toxopneustes 9 x Hipponoe S cross, 

 and the reciprocal were easily made after allowing the eggs to stand in 

 sea-water for some hours after fertilization. In the embryos of both 

 crosses made in ordinary sea- water, which was alkaline, the Hipponoe 

 influence showed a tendency to predominate. In the embryos of both 

 crosses made in sea-water of increased alkalinity, there was evidence of 

 an increase in Hipponoe influence. In the embryos of both crosses 

 made in sea-water of decreased alkanity, a tendency toward Toxopneustes 

 dominance was evident. The results thus show Hipponoe dominance 

 in sea-water of a higher OH ion concentration, and Toxopneustes 

 dominance in sea-water of a lower OH ion concentration. 



It is suggested that these variations in the alkalinity of sea-water, 

 brought about artificially in the laboratory, may correspond to normal 

 seasonal changes. If this be true, the winter (paternal) embryos and the 

 summer (maternal) plutei of the combination Spheerechinus x Strongylo- 

 centrotus of other investigators had their origin in such normal seasonal 

 changes of OH ion concentration. 



The results of this and other investigations show species tendencies 

 towards different grades of temperature and alkalinity. The explanation 

 of the preponderance of one character over another in Echinoderm 

 hybrids seems to be in the reaction of the species towards a complex of 

 factors. 



Early Stages of Development in Echinoderms.§— Julius Schaxel 

 describes the structure of the ovary, the maturation, the cleavage, the 



* Bull. Soc. Zool. France, xxxv. (1910) pp. 122. 



t Anuot. Zool. Japon, vii. (1910) pp. 213-18 (8 figs.). 



% Publications Carnegie Inst. Washington, No. 132 (1910) pp. 117-51 (6 pis.). 



§ Arch. Mikr. Anat., lxxvi. (1911) pp. 543-607 (5 pis. and 8 figs.). 



