20 



The authors have proved (1889) that in Aspidoecia the male is hinged by a thread 

 which proceeds from a hole on the ventral side of the front part of the head: »ce filament 

 est secret par deux grosses glandes cementaires probablement homologues de celles qui 

 servent a la fixation chez les Cirripedes«. No doubt it is this comparison on which they 

 base their opinion that the genital aperture is found on the head, and also that the spermatic 

 glands secrete the viscous substance which forms the thread, as these organs are believed 

 to perform this double function in theCirripeds 1 ). A slight basis indeed for such remarkable 

 statements! The observation about the hingement of the male is correct, but then, has the 

 thread to disappear in order to allow the spermatophores to come out of the hole, or is the 

 order of the two processes to be inverted, or does the male possess another genital aperture 

 on its front near the base of the thread? Unfortunately we get no answer to all these 

 legitimate questions — though indeed we can scarcely imagine any possibility besides these 

 three. No, the doctrines about the genital aperture on the head and the double function of 

 the sexual organs in the Choniostomatidae are postulates without any foundation. Within 

 the family mentioned it is an ordinary phenomenon to find the male attached by a thread; 

 this prevents it from being washed away and allows it to creep as far as the thread can 

 reach, giving it frequent opportunities to fix its spermatophores on the entrances to the 

 receptacula seminis. Besides, the genital aperture is not found on the head; in Sphceronella 

 paradoxa I have been able to prove the existence of two genital apertures at a short 

 distance from each other on the ventral side of the trunk: from each spermatotheca proceeds 

 an efferent duct forward and obliquely towards the median line, and these canals open on 

 the posterior side of the depression between the first pair of trunk-legs, or at least somewhat 

 behind the basis of the maxillipeds. But then, what remains of the hypotheses advanced as 

 facts by the two authors, that the genital aperture of the male in the Choniostoniatida} is found on 

 the head, and that the »canaux g6nitaux« secrete the viscous substance by which the animal 

 attaches itself? Nothing, absolutely nothing ! And what remains of their best proof- based 

 on these organs — , that Ohoniostomatidse and Herpyllobiidas ought to be grouped in one 

 family? Equally: nothing I except a rather surprising impression of the loose method of the 

 authors: to establish unreliable conjectures as facts in order to prove an absurdity. 



Though I suppose that most readers have now formed a pretty clear idea of the 

 great differences between the two families, I will give a summary. The likeness between 

 the two families is limited to the following features: both are parasitic Copepoda, in which 

 the males are several or many times smaller than the females; in both sexes the body is 

 small, sub-globular or oblong; the last larval stage of Herpyllobiidae is the first Cyclops 

 stage, it resembles to a certain degree the larva just coming out of the egg in the Cho- 



J ) I will not here enter upon criticisms which have appeared elsewhere about Darwin's unfortunate 

 statements upon this subject, nor on Giard's later suggestions concerning Rhizocephala. 



