

ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 357 



cylindrical form, about 105 /* in length by 25 /u, in breadth ; it is com- 

 pletely covered with cilia ; the ectoderm cells are disposed in regular 

 annuli and enclose whitish refractive granules; the interior is filled with 

 a genital mass containing embryos at different stages of development. 

 The species is hermaphrodite and autogamous, and the same is probably 

 true of the new variety, which differs from the type in the number of 

 rings and the dimensions of parent and embryos. 



Development of Tardigrada.*— Wanda von Wenck has studied the 

 embryonic and post-embryonic development of Macrobiotus lacustris 

 Duj. The segmentation is total and approximately equal. The result 

 is a morula. The endoderm is formed by delamination from the morula. 

 The blastopore is formed later and with it the lumen of the archenteron. 

 Just in front of the blastopore the primary germ-cells arise from the 

 outer layer and pass into the ventral wall' of the archenteron. The 

 post-embryonic development is very simple : there are successive moults 

 without metamorphosis. The tooth apparatus may be renewed at a 

 moult, as Reukauf observed. The chitinous parts of the tooth apparatus 

 are formed by the paired organs called " salivary glands " which lie on 

 the sides of the oesophagus. Encystation may occur at various ages. 

 The organs do not undergo histolysis in the encystation, as Murray 

 supposed. The possible affinities of Tardigrada are discussed, but no 

 definite conclusion is arrived at. 



Echinoderma. 



Artificial Parthenogenesis in Sea-urchin Ova.f — M. Herlant has 

 experimented with Paracentrotus lividus, and follows Loeb in recogniz- 

 ing the operation of two successive factors, the first a fatty acid, which 

 determines the activation of the ovum and the appearance of a strong 

 irradiation around the female pronucleus ; the second a hypertonic 

 solution which induces the appearance of accessory asters. Herlant finds 

 that the activation brings about the development of at least two succes- 

 sive cycles of irradiations, formed around the female pronucleus by the 

 rhythmic activity of its centrosome. Th3 essential action of the hyper- 

 tonic solution is to bring about the formation of one to three accessory 

 asters. This depends not only on the duration of the hypertonic treat- 

 ment, but also on a special aptitude which the ovum acquires progres- 

 sively during its activation. This aptitude reaches a maximum and then 

 wanes and disappears. 



Coelentera. 



Hydrozoa benthonica.l— Hjalmar Broch reports on a collection of 

 benthonic Hydrozoa from the West African coast, from Cape Verde 

 to the mouth of the Orange River. The collection includes two new 

 species of Hydractinia, Hebella michaelsenisp. n., Sertularia hupferi sp. n., 



* Zool. Jahrb. Abth. Anat., xxvii. (1914) pp. 465-514 (4 pis. and 10 figs.). 

 t Comptes Rendus, clviii. (1914) pp. 1531-3. 



X Beitrage zur Kenntniss der Meeresfauna Westafrikas, Hamburg, 1914, pp. 

 21-50 (1 pi. and 12 figs.). 



