GO SUMMARY OF CURRENT RESEARCHES RELATING TO 



animal is capable of making the most various changes in the form of its 

 body, it may be referred to the arrangement general among Pneunia- 

 tophora. 



The supporting lamella of tho air-umbrella gradually widens out and 

 forms a considerable layer, which in section is seen to be concentrically 

 striated ; it is clearly secreted by ectoderm cells. The pneumatophoro 

 early takes on its characteristic triangular form, which is especially 

 distinct throughout life in P. utriculus. Various parts of the author's 

 description will bo more easily comprehended when they appear in tho 

 promised illustrated memoir. 



Influence of Salinity.* — Ilerr C. F. W. Krukenberg has made an 

 elaborato series of experiments on the relation of the salt content of 

 Medusae to the salinity of the surrounding water. (1) The fluid in tho 

 disc always closely corresponds in salinity to the surrounding water ; in 

 waters with less salt, however, the salinity of the disc bears a much greater 

 proportion to that of the water than occurs in the Medusae of Salter seas. 

 (2) From the examination of seven different forms of Medusa, it was 

 seen that in regard to the salinity of the water leaving the disc no 

 noteworthy differences obtained. (3) There is no evidence to suggest 

 that the salinity of the disc in salt seas can sink below that of the 

 surrounding water without danger to life. The study of Red Sea forms 

 showed on the contrary that as long as the external salinity does not 

 exercise any injurious influence on the life of the organism the internal 

 salinity is always greater than that of the water. 



Krukenberg has made a very extensive series of experiments, of 

 which the tabulated results are given, on the loss of water when the 

 Medusae are removed from their medium, and on the influence of 

 numerous reagents. (1) The loss of water, which takes place by a 

 special process, occurs much more rapidly in air than in sea or distilled 

 water. (2) It is much more rapid in the first hours of exposure to dry 

 air. (3) The loss, especially at first, is greater in distilled than in sea- 

 water. The influence of numerous reagents on the loss of water is then 

 chronicled. 



Finally, the author sums up all the various ways in which water 

 may pass into or out of an organism, and inquires how it passes out in 

 Medusae. He regards it as quite certain that diffusion has nothing 

 to do with the process. The water passes in by absorption, but 

 Krukenberg is unable to decide whether it passes out by exudation or 

 in a purely mechanical fashion, or by both combined. 



Colours of Corals.f — Dr. C. F. W. Krukenberg has made a study of 

 the colours of the living corals in the Red Sea. It is well known that 

 the coral banks afford a feast of colour hardly to be surpassed by any 

 other of nature's displays. The species which he investigated were 

 Stylophora subseriata Ehrbg., Pocillopora hemprichi Ehrbg., Seriatopora 

 spinosa M. E. and H., Madrepora haimei M. E. and H., Favia ehrenbergi 

 Klz., Galaxea irregularis M. E. and H., Montipora tuberosa Klz., 

 Turbinaria conica Klz., and Tubipora hemprichi Ehrbg. 



In these species Krukenberg found the following pigments : — (1) the 

 yellowish-brown colouring matter of the so called " yellow cells " of 

 the Actinidee, which exhibits a deceptive resemblance to the hepatochrome 



* Vergl. Physiol. Studien, II. Reihe, 4 Abth. (1887) pp. 1-58. 

 t Ibid., pp. 172-87 (1 pi.). 



