554 General Notes. \JA2y, 



least of the chromatophores is to diminish the transparency of the 

 skin and thus to lower the action of even moderate light when it 

 begins to affect injuriously the organism. 



The Metamorphosis of Peneus. — Dr. W. K. Brooks, in his 

 account of the metamorphosis of Peneus (Johns Hopkins Univer- 

 sity Circulars, Nov., 1882), noticed in the January number of 

 the Naturalist (p. 90), says : 



"Those familiar with the literature of the subject will recollect 

 that Fritz Miiller kept under observation until it changed into a 

 protozoea, a nauplius which he captured at the surface of the 

 ocean. He also secured, in the ocean, a very complete series of 

 larvae, through which he identified his protozoea with a young 

 Macrouran with the characteristics of the genus Peneus. He did 

 not rear the nauplius from the Peneus egg, nor did he actually ob- 

 serve the transformation into the young Peneus. Certain over- 

 cautious naturalists have therefore refused to accept his conclu- 

 sions until more conclusive proof should be furnished." 



Dr. Brooks then proceeds to state that he has captured the pro- 

 tozoea of Peneus and reared it in confinement, witnessing every 

 one of the five molts between the youngest protozoea and the 

 young Peneus. " The whole metamorphosis of Peneus has 

 therefore been actually witnessed and there is no longer any room 

 for criticism." 



If Dr. Brooks will read Fritz Miiller's two papers on the subject 

 (Arch. Naturgesch., Bd. xxix.,Zeitschr. wissensch. Z06L, Bd. xxx), 

 he will learn that Miiller did not keep the nauplius under obser- 

 vation until it changed into a protozoea, but that he captured the 

 protozoea in the sea and inferred its relation with the nauplius 

 from its likeness in movements, color and structure. This as- 

 sumed relation between the protozoea and the nauplius " certain 

 over-cautious naturalists" wished to see proved either by hatching 

 the nauplius from the egg of Peneus, witnessing the transformation 

 of the nauplius into the protozoea, or discovering intermediate 

 stages between the nauplius and the protozoea. Brooks' observa- 

 tions have no bearing on the question whatever. He has proved 

 the connection between the stages older than the nauplius. 

 That the nauplius belongs to the same series, he has not shown. 

 In fact, his youngest protozoea is an older stage than the youngest 

 protozoea secured by Miiller. He has riveted the links in Miiller's 

 chain that were closely joined before, but has not touched the 

 weak spot ! 



From the complete disappearance of the exopodites from the 

 five pairs of legs and the simplicity of the abdominal appendages 

 in the oldest stage observed, it would appear that Brooks' larva 

 belongs to the genus Sycionia rather than to Peneus. 



The larval stages of the Peneidae seem to be not uncom- 

 mon in the warmer seas. Besides the published figures of Miiller 



