80 Mr. C. Spence Bate on the 



that are to be accepted as facts should be establislied on obser- 

 vations that can leave us no doubt. 



Unfortunately, on our coasts there is but one species of 

 Penceus (P. caramote) ^ wadi this appears to be rather a Mediter- 

 ranean form that occasionally strays as far as our southern 

 shores than a local species. 



We might have supposed, as in the warmer seas several 

 species are abundant, that some one would have been able 

 during these last fifteen years to capture a specimen that was 

 carrying ova so nearly approaching the period of hatching 

 that Fritz Miiller's conclusions might have been demonstrated : 

 he would then not have had occasion to say, " if my Nauplius 

 be not derived from a Penceus^ and is not to become a Penceus^ 

 let my opponents tell me what possibly it can be." 



Certainly exception should be taken to the word " op- 

 ponent ;" the only object that any truly sincere observer 

 can have is to establish the truth. If the Nauplius form be 

 that of a young of Penceus or any other prawn, it is only 

 a question of time for us to know the fact. As yet the 

 young of Penceus is not known ; and Fritz Muller says that 

 they who wish it demonstrated should tell him Avhat his 

 Nauplius is the young of. This can only be done when the 

 larval forms of all prawns, including Penceus, are known by 

 direct evidence. We shall therefore be approximating to the 

 knowledge of this by showing what forms do not quit the 

 ovum as larvas in the Nauplius condition. 



Some few years since. Dr. Power was attached to a regi- 

 ment stationed in the Mauritius. During his period of resi- 

 dence in that island he occupied himself with collecting the 

 various forms of Crustacea, and hatched many. These speci- 

 mens he preserved, both adults and larv«, and forwarded them 

 to me. It formed the basis of a paper to the Royal Society, 

 a short abstract of which appeared in the ^ Proceedings' (No. 

 168, March 9th, 1876, p. 375*). Of the Macrurous forms we 

 can say with confidence that neither the young of Palcemon, 

 of which there is a freshwater species on the Island of Mauri- 

 tius, as well as our European form, nor Bippolyte, Caradina, 

 Crangon, Alphceus, Homaralphceus, n. g., Uomarus, Stenopus, 

 Hymenocera, Palinurus, Squilla, nor Asfacus quits the ovum in 

 the Naupilius condition. To these I can now add some of the 

 deep-sea forms, including Willemoesia, that were taken during 

 the ' Challenger ' expedition. But this still leaves the ques- 



• A year previous to the publication of Prof. Claus's memoir ' Unter- 

 Buchungeu zur Ei-forscbung der genealogi.schen Grundlage des Crustaceen- 

 Svstcms.' 



