346 Mr. J. W. Fewkes on a Method of 



Umgebung der beiclen hornformigen Canale des Oelbetialters 

 und spaterhin auch von den Ecken beginnend in der gesamm- 

 ten Gallerte eine weissliche Triibung auftritt. Dieselbe 

 beruht auf dera Erscheinen ausserordentlich feiner Kornclien, 

 die wieder (nach etvva einer lialben Stunde) versclivvinden, 

 wenn die Eudoxie der Ruhe liberlassen wird. Die eigen- 

 thiindiche Triibung erinnert an eine analoger Ersclieinung 

 bei Hippopodius nur dass liier die auf einen Reiz erfolgende 

 und spjiter verschwindende milchige Farbung an die Ekto- 

 dermzellen der Schwimmglocken gebunden ist. In gevvissem 

 Sinne muss selbst die structurlose Gallerte des Deckstiickes 

 einem Ileize zuganglich sein, wie das allmaliliclie Auftauclien 

 und ebenso langsame Verscliwinden einer ziemlich intensiveu 

 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 "cjstons" or tasters with a 

 terminal opening has been noticed by several authors. Both 

 KoUiker and Leuckart speak of it, although they seem to 

 regard the discharge as due to a rupture of the wall rather 

 than [as taking ])lace] through a normal terminal opening. 

 KoUiker says, " Ohne Zweifel ist diese iSubstanz ein Excre- 

 tionstoflf, doch wird ohne genauer Kenntniss ihrer chemischen 

 Beschaffenheit nichts Niiheres liber ihre Bedeutung beizu- 

 bringen sein." 



Hteckel describes the structure of these Cystous 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 Apolemidee, Agalmida?, and Forskalidae. 



The " cystous " or hydrocysts with " months " in the 

 Agalmidse are often, according to Hseckel {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." 



Hjsckel ofiers the following explanation of the phenomenon 

 in Forskalia : — " The excretion of the pigment-masses and 



