Parasitic Crustacea effect their Conservation, 273 



true in this case : either chance presides in this union of the 

 young Crustacean to its mother, or it has nothing to do 

 with it. 



On the former hypothesis, as the embryo must be either male 

 or female, it is evident that it may sometimes be a male, and 

 then matters would go on as above described; if, on the con- 

 ti-ary, it is a female, the conditions of which I have just spoken 

 would certainly no longer exist, but this migration would still 

 have a very useful purpose, since it would transport from one 

 fish to another a young Crustacean, which perhaps might have 

 been unable to perform this migration of itself and by its own 

 powers, and thus contribute to dissemination, which is one of 

 the most essential elements in the conservation of the species ; 

 moreover, there is nothing against these females meeting with 

 males in their new position. 



The second supposition is the most probable one, in my 

 opinion. Indeed, how can we explain the development of so 

 extraordinary an apparatus at the anterior part of the frontal 

 margin of these young Crustacea without assuming some im- 

 portant motive for the production of this modiHcation ? and 

 no reason can well possess more importance than the con- 

 servation of the species. Moreover it would be very difficult 

 for creatures so feeble and so destitute of organs of adhesion to 

 maintain their position and resist the action of the waves, which 

 is the more powerful in proportion to the rapidity of progression 

 of the tish on which they occur. 



However this may be, I leave these facts as ascertained by me 

 for the appreciation of those who are willing to seek for their 

 solution, which, however, in my opinion, can hardly be other 

 than that indicated by me. 



As already stated, the frontal cord is very flexible, especially 

 in its middle part ; it is hollow, cylindrical, and covered with a 

 few hairs, and becomes rigid and brittle near the frontal margin ; 

 so that it might be broken before the proper time, if another 

 combination had not been made to avoid the possibility of such 

 accidents. 



In most of the young Crustacea furnished with this apparatus 

 there exists an articulation below the antenna; and the eyes, 

 which allows this part of the head to bend as if it were borne 

 upon a neck ; so that by this means sudden and violent shocks 

 are avoided, as well as the accidents which might be produced 

 by them. A time comes, however, when rupture is neces- 

 sary, — namely, when the young Crustacean, becoming able to 

 procure its own nourishment, has no longer any need of its 

 mother. It then takes place close to the frontal margin, where 

 here is a sort of umbilicus, which subsequently diminishes and 



Am. i^ Mag. N. Hist. Ser.3. Vol. xiv. 18 



