108 Prof. Miiller on the Production 



the inexplicable point. Upon this view we hazard much less 

 than by adopting the others ; and T believe that in the course of 

 further investigations we must hold fast by it, until the whole 

 process has been made clear by direct observation." 



It is very remarkable, that while thus decisively admitting 

 the probability that we have to do with a case of parasitism, 

 Prof. Miiller does not go a step further, and inquire in the first 

 place, whether the structure of the sac has any analogy with that 

 of any known molluscous organism; and secondly, whether the 

 mode of parasitism is analogous to other cases. We have already 

 endeavoured to answer the latter question in the affirmative ; — • 

 can the former be similarly answered ? 



"The question (says the Professor} is, to conceive a sexually 

 perfect mollusk which has laid aside all molluscous characters ; 

 which has neither organs of sense, foot, liver, anus, heart, vessels, 

 nor sexual organs of gasteropod or mollusk, and yet which pos- 

 sesses the faculty of discovering a particular vessel in another 

 animal, and of nourishing itself on the blood therein contained." 

 (Archiv, p. 25.) 



A riddle, truly, that the Sphinx might have propounded ; and 

 it is not without some wholesome fear of being devoured, that 

 we venture to suggest a possible mode of solution. 



In our previous remarks, the possibility of an affirmative 

 answer to this question was but indicated, in an allusion to the 

 structure of Hectocotylus, inasmuch as we did not doubt that 

 Prof. Miiller himself would consider the subject from this point 

 of view also. He has not done so however, and it is therefore 

 necessary to explain the meaning of that allusion more fully. 



Hectocotylus Argonauta is developed from certain ova of the 

 Argonaut. It is therefore homologous with a complete mollusk, 

 not with a spermatophore. It consists of a muscular tube beset 

 externally with two rows of suckers. There are no gills, and there 

 is no separate abdomen. 



If there be any intestine, it is a csecal tube opening anteriorly 

 by a small aperture ; at least, such an organ exists in the Hecto- 

 cotylus Tremoctopodis, in which species also a heart, gills, and 

 traces of a nervous system were observed. 



The testis is a delicate glassy vesicle containing spermatozoa. 



These Hectocotyli, which may thus almost be said to " have 



laid aside all molluscous characters," are yet the males of the 



Cephalopods to whose mantle, cavity, or arms they parasitically 



adhere. 



Suppose now, that the mollusks developed within the mol- 

 luskigerous sac are not unisexual like the Cephalopods, but her- 

 maphrodite ; that after swimming freely for a while like most 

 mollusk-larvse (a stage which would correspond to the Cercaria 



