300 NATURAL SCIENCE. April. 



KBr, KI, KNOy, K0SO4, Nal, NaNO:^, MgSO^ gave somewhat similar 

 results. It is therefore possible by adding these salts to the sea- 

 water to disturb the metabolic processes by which the calcareous 

 skeleton is formed and the growth by which the peculiar Pluteus 

 processes are formed, while the fore-, mid-, and hind-gut, the vaso- 

 peritoneal vesicles, and the ring of cilia, develop uninfluenced. 



The inhibition of the characteristic Pluteus outgrowths is inter- 

 preted by Herr Herbst as due to absence of the requisite stimulus 

 naturally provided by the calcareous rods ; for he believes, it seems 

 to me with much likelihood, that the rods afford a stimulus to growth 

 in those parts where they occur. 



When the solutions of the added salts were made in distilled 

 water, with the obvious result of reducing the amount of lime in the 

 aquarium, no needles of lime were formed even by the seventeenth 

 day, although the cells which ought to have contributed to form 

 them were then seen arranged in their typical disposition. 



Another remarkable result was the production of larvae (gastrulae) 

 in which the tuft of long, stiff processes, which normally occurs at the 

 so-called animal pole, and is probably directive, was hypertrophied 

 into a protruding knob with small mobile cilia. This observation was 

 made at Trieste in 1891, but it did not succeed at Naples in 1892, nor 

 again at Trieste in 1892, a divergence which the observer accounts 

 for by the different temperature-conditions which obtained. 



But, perhaps, the most remarkable results which Herr Herbst 

 was able to make sure of, were obtained by adding salts of Lithium 

 to the sea-water. The normal blastula elongates, constricts into two 

 portions — one thin- walled, the other thick- walled. They differ also 

 in pigmentation and ciliation. Between these two primary parts a 

 connecting region is formed. In the majority no calcareous needles 

 appeared. Very frequently the thick-walled portion grows at the 

 expense of the thin-walled portion, which dwindles to a mere cap. In 

 rare cases a gut and a mouth appeared. Now, had these larvae lived 

 a little longer, it seems quite likely that they would have reached the 

 Pluteus stage to which they were approximating. If so, they would 

 have reached it by an entirely abnormal path. But, without making 

 any suppositions, the results are remarkable enough. It seems that 

 the thick-walled portion is nothing more nor less than the protruded 

 archenteron — a sort of embryonic hernia ; that the thin-walled portion 

 is the outer wall of the gastrula, and that the connecting portion is the 

 hind-gut of the Pluteus. 



It is interesting to observe that the potency of the Lithium salts 

 decreases from the Chloride to the Iodide ; in fact the potency is in 

 inverse ratio to the molecular weight. So is it also with salts of 

 Sodium and Potassium. The rule only applies to salts of one and 

 the same metal. 



It seems to have been this fact, taken along with researches of 

 Hofmeister, Heidenhain, and others, that led Herr Herbst to the 



