300 NATURAL SCIENCE. APRIL, 
KBr, KI, KNO,, K,SO,, 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 larve (gastrule) 
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 larve 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 
