346 Mr. J. W. Fewkes on a Method of 
Umgebung der beiden hornférmigen Caniile des Oelbehiilters 
und spiiterhin auch von den Ecken beginnend in der gesamm- 
ten Gallerte eine weissliche Triibung auftritt. Dieselbe 
beruht auf dem Erscheinen ausserordentlich feiner K6rnchen, 
die wieder (nach etwa einer halben Stunde) verschwinden, 
wenn die Eudoxie der Ruhe iiberlassen wird. Die eigen- 
thiimliche Triibung erinnert an eine analoger Erscheinung 
bei Hippopodius nur dass hier die auf einen Reiz erfolgende 
und spiter verschwindende milchige Fiarbung an die Kkto- 
dermzellen der Schwimmglocken gebunden ist. In gewissem 
Sinne muss selbst die structurlose Gallerte des Deckstiickes 
einem Reize zuginglich sein, wie das allmiihliche Auftauchen 
und ebenso langsame Verschwinden einer ziemlich intensiven 
Triibung beweist.” 
We might possibly compare this phenomenon with the 
cutaneous circulation and change of colour in pelagic fish- 
embryos and in Cephalopoda; but we know so little of the 
organs by which it is produced that one can as yet hardly 
venture an explanation. 
The excretion and discharge of a coloured fluid from those 
organs which are known as ‘“cystons” or tasters with a 
terminal opening has been noticed by several authors. Both 
K@élliker and Leuckart speak of it, although they seem to 
regard the discharge as due to a rupture of the wall rather 
than [as taking place] through a normal terminal opening. 
Kélliker says, ‘‘ Ohne Zweitel ist diese Substanz ein Excre- 
tionstoff, doch wird ohne genauer Kenntniss ihrer chemischen 
Beschaffenheit nichts Niaheres tiber ihre Bedeutung beizu- 
bringen sein.” 
Heckel describes the structure of these Cystons or “ anal 
vesicles,” showing that they are excretory organs with a ter- 
: =) 
minal anus and glandular walls often highly coloured. They 
are, according to him, confined to the Physophores, mainly 
to the Apolemide, Agalmide, and Forskalide. 
The ‘cystons” or hydrocysts with “mouths” in the 
Agalmide are often, according to Heckel (op. cit. p. 219), 
coloured red or brown, and “the fluid secretion, or the pig- 
mented granular or crystalline masses secreted by it, are 
ejected by the distal mouth, or, rather, the anal opening, 
which is closed by a muscular sphincter.” In the genus 
Forskalia the same author says, ‘‘ When a quietly floating 
forskalia is touched it suddenly discharges the contents of 
the chromadenia [pigment-glands| and makes the surrounding 
water dark and intransparent.” 
Heckel offers the following explanation of the phenomenon 
in Forskalia :—“ The excretion of the pigment-masses and 
