448 THE VOYAGE OF H.M.S. CHALLENGER. 



pointed and narrow extremity falling forwards ready for insertion when the opportunity 

 occurs. 



The second pair of pleopoda carries, attached to the base of the inner of the two 

 rami, a rigid branch that is about a third of the length of the one to which it is attached. 

 The object of this, which is only present in male animals, is not very obvious, and it is 

 only a conjecture, when I say that it maybe useful in adding power to retain the preceding 

 pair in position during copulation. 



When the spermatophore is liberated from the influence of the male animal, the 

 smaller extremity is inserted into the oviduct and there retained, the ova being fertilised 

 as they pass through the seminal receptacle, which opens on the inner side of the third 

 pair of pereiopoda (PI. LXXXI. figs. 1?, 2?). 



This latter organ I have not been able in the specimens at my command to determine 

 to be of the inverted bottle-shaped form as figured by Professor Brooks ; nor does it 

 appear to open anterior to the third pair of pereipoda, but according to my observation it 

 is only a slight enlargement with a constriction, or rather a series of constrictions, that 

 forms a series of chambers in the oviduct. 



Professor Brooks says that there is only one opening, and his opportunity and power 

 of observation are so great that they demand assent, but I can only state, according to the 

 opportunities of my own observation, that the neural cord, which consists of an elongated 

 mass with bulbs increasing in size from the oral appendages to the third pair of 

 pereiopoda, whence it continues as a fine thread until it reaches the first pair of 

 pleopoda, passes behind or rather on one side of the ovisac, and therefore the neural cord 

 being in the median line the ovisac must be on one side ; that on the opposite side, as in 

 the males, is probably obsolete or only periodically in use. 



The ovaries are very long, and in some specimens reach as far back as nearly to 

 the middle of the sixth somite of the pleon (fig. 1?), where they terminate in a gradually 

 narrowing point ; the posterior portion is full of simple granules, and the anterior with 

 gradually ripening ova. 



Observations. — So far as I can determine, there are only two species of Lucifer, and 

 these are probably the same as recorded by Milne-Edwards in his short description. All 

 other forms, of which I give several figures, are, I believe, only dependent upon variation 

 in the progress of development. Even the two recognised species differ but little in 

 important characters. The ophthalmopoda of one are longer than those of the other, and 

 the form of the teeth on the lateral margins of the sixth somite of the pleon in the males 

 varies but Httle. The other external features of difference are not very considerable. The 

 last mentioned difference only exists in the male animals, whereas the females closely 

 resemble one another in both species, except in the relative length of the ophthalmopoda. 



Dana, in his Report on the Crustacea of the U.S. Exploring Expedition, describes 



