INVERTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 441 



incessantly undergoes changes in form ; the significance of these 

 movements seems to lie in this, that after the extrusion of the polar 

 globule the creature presents an example of atavism inasmuch as the 

 Amoeba phase is continued on till the Synamceba phase commences to 

 exhibit itself. The gastrula is formed by " epiboly " ; during the 

 segmentation the nuclear protoplasm is alone active, the cellular 

 remains i)assive ; when the centre of the amphiaster coincides with 

 that of ths cell, and when the two axes correspond or are set 

 obliquely, the two asters are equal, and the plane of segmentation is 

 perpendicular to the axis of the amphiaster and divides it into two equal 

 parts ; but when the centres do nut correspond, &c., the two asters 

 are unequal, the smaller aster is that which is further from the 

 centre, and the plane of segmentation divides the axis of the amphi- 

 aster into two unequal parts, and these parts arc unequal in proportion 

 to the difference in the attractive forces of the two asters. 



The mesoderm is formed at the expense of four large endodermal 

 cells at the o^-al pole, and before they unite into a continuous layer 

 they form four primitive lines. An interesting point is the appear- 

 ance of a fifth endodermal sphere, which becomes intercalated among 

 the rest. It is only during development that the Ehabdocoelous 

 intestine takes on, in the Dendrocoela, a dendritic form. The ectoderm 

 is differentiated, as is the mestjderm, into two layers ; the inner one 

 of the former is that which gives rise to the " rods," and of the latter 

 that which forms the reticulum which so greatly occupies the body 

 cavity. 



Turbellaria of Prague.* — Dr. Vejdovsky states that the Tur- 

 bellaria form a very characteristic component of the fauna of the 

 springs of Prague. Among tlie Mcsostomidte he has found a new 

 species which he designates M. HaUezianum ; it \\ as found in dark 

 spots, is snow-white, and has no eyes. Stcnodomum ignavum n. sp. 

 was found with JEolosoma tenehrarum, also a nevv species, and is easily 

 distinguished from S. unicolor, at least by its much larger cbitinous 

 corpuscles and by its rods. In the S. leiicops of authors he has 

 discovered an oval gland which lies in the pharyngeal region over the 

 water-vascular system, and is provided with a short eticrent duct 

 which opens to the exterior behind the central ganglion ; it appears 

 to belong to the generative apparatus and is regarded, so far as its 

 orifice is concerned, as homologous with the cephalic pore of the 

 Oligochaita. 



New Parasitic Rhabdocoele.t — Graffilla muricicola, the subject of 

 Dr. von Ihcring's paper, is fuund as a j)arasitc in the renal organ of 

 Murex trunculus and M. hrnndarix, where it is easily distinguishiiblo 

 owing to its reddish-brown colonition. This discovery is very interest- 

 ing as the number of parasitic Turbellaria as yet known is exceedingly 

 small. The species in question, which sometimes attains to a length of 

 5 mm. is remarkable among its congeners from having a thick 



* [Sop. rcpt.] 'SB. K. Bohm. Gesoll. Wisa. Prag/ 1879, p. 501. 

 t 'Zuit.sclir. wisa. Zool.,' xxxiv. (1880) p. 147. 



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