the Mouth in Sucking Crustacea. 21 



part some few hooks — the middle one three, the innermost 

 only one. 



In the male Cymothoa the sides of the month-tube are, as 

 we have stated, supplied by the maxilliped-palps, which 

 reach as far as the labrum ; and the maxillary lobes of the 

 second pair have therefore here, as in ^ga^ no other duty 

 than to fill up the slit between the maxilliped-palps, though 

 certainly this opening is proportionally larger in Cymothoa^, 

 the palpi in question being smaller and the lobes of the maxil- 

 lipeds wanting. But in the female Cymothoa^ where the 

 maxillipeds do not enter into the construction of the mouth- 

 tube, this devolves entirely on the second pair of maxillae 

 (x*, fig. 6 a ; the maxillipeds are removed). These are there- 

 fore much broader than in the male ; their stems meet in much 

 greater extent, namely with the whole of their front halves, 

 and the lobes form together a large curved lip, which, on the 

 sides, joins the labrum. 



Although this conversion of the maxillary lobes of the 

 second pair into a kind of lip in all essential points makes up 

 for the non-participation of the maxillipeds in the construc- 

 tion of the mouth-tube in the female, and their limited parti- 

 cipation in the male, this expedient would, nevertheless, not 

 be sufficient if the labrum in Cymothoa were not larger than 

 in jEga. But whilst in this latter genus the labrum occupies 

 only one-third of the circumference of the mouth-tube, it sup- 

 plies in Cymothoa quite one-half. It is consequently much 

 broader, much more considerably arched from the top down- 

 wards, so that it becomes like an inverted cup when the mouth- 

 tube is contracted; a small undulation is then also observed 

 in the middle of the margin, which latter is furnished with 

 numerous minute warts. But when the mouth-tube is dis- 

 tended and examined from beneath, the margin appears undu- 

 lated or crenate. 



From all this it appears that the mouth-tube is, upon the 

 whole, softer and less powerfully armed in Cymothoa than in 

 ^ga : instead of the almost fringe-like covering of warts on 

 the labrum, the considerable bundle of hooked spines on the 

 palpi of the maxillipeds, and the row of spines on the turned- 

 over margin of the maxillary lobe of the second pair in ^Ega, 

 we find in Cymothoa merely the very minute warts on the very 

 edge of the labrum and on the cushion-like lobes of the second 

 pair of maxillae, and the very short row of hooked spines on the 

 two innermost cushions of these lobes and on the margin of 

 the terminal joint of the maxilliped-palpi in the male. But 

 this weaker armature of the mouth in Cymothoa of course cor- 



