176 SUMMARY OF CURRENT RESEARCHES RELATING TO 



cells, grow in size and diminish in number, till at last they are 

 so extensive that nothing but thin partitions intervene between 

 them. 



The anterior endodermal sacs undergo development asymmetri- 

 cally ; they become shut off from the exterior, the one on the right 

 increases in size, while the left undergoes no change, till at the com- 

 mencement of larval life it opens on the left side of the body by a 

 small orifice. This is the special organ of larval life, as described by 

 Kowalevsky. Another organ, the club-shaped gland, is also developed 

 from the exterior. Formed in the region of the first metamere, it 

 becomes towards the end of embryonic life shut off from the exterior. 

 It now lies chiefly on the right side, but extends transversely across 

 the enteric canal, and opens at the outer margin of the mouth ; part of 

 it becomes glandular, and the rest forms an efferent duct. The 

 external epithelium is still ciliated, but is now generally thinner. 



In the fifth period, the last here described, those changes occur 

 which enable the embryo to pass into the larva. A number of orifices 

 are now formed, the mouth and the first gill-cleft, the orifice of the 

 ciliated organ (or left endodermal sac), the club-shaped gland, and 

 the anus. The body meanwhile increases in length, fresh segments 

 being formed, a number of strong motile flagella may be seen to be 

 developed from the cells, and all the tissues of the body are now 

 formed of transparent protoplasm. 



B. INVERTEBRATA. 



Fossil Organisms in Meteorites* — In his own abstract of his 

 detailed memoir on this subject, C. Vogt says, " I have endeavoured 

 to discover whether the bodies to which Dr. O. Hahn calls attention,! 

 really have the structural characters of the organisms to which he has 

 assigned them. 



" By a detailed comparison of the living and fossil sponges with 

 the supposed sponges of meteorites, I am able to show that there is no 

 resemblance in microscopical structure between them. I prove, by 

 the same method, that neither the corals nor the Crinoids which 

 Hahn believes that he has discovered in the meteorites have anything 

 in their microscopic structure in common with living or fossil corals 

 or Crinoids. I further refute the theory, which may be described as 

 at least singular, according to which the corals are only an evolutional 

 development of the sponges, and Crinoids a product of the further 

 evolution of the corals. 



" I demonstrate the fact that, in order to obtain the completest 

 possible knowledge of the structure of the chondrites " (the species of 

 meteorites from which the specimens were prepared) " we must resort 

 to check-experiments, based on dissociation of the constituent elements 

 either by chemical reagents (as acids and caustic potash) or by the 

 mechanical operation of grinding to the finest possible sections. The 

 fragments which are obtained in this way should be studied by 



* Comptes Rendus, xciii. (1881) pp. 1166-8. 

 t See this Journal, i. (1881) pp. 722-4. 



