one, two, or three pairs. 



In the chapter on development, metamor- 

 phoses, and genealogy. Professor Packard 

 gives a short account of the naiiplius form in 

 Phyllopoda as an introduction to Dr. Gissler's 

 interesting notes in the following chapter, and 

 then briefly discusses the ph3-logeny of the 

 group, in which he appears to find but one dif- 

 ficulty. He savs, — 



" The diflflculty is (and this is a point ap- 

 parently overlooked by Fritz Miiller, Dohrn, 

 Claus, and Balfour) to account for the origina- 

 tion of the phyllopods at all from any marine 

 forms. The onlj' explanation we can suggest, 

 is that the phyllopods have arisen through 

 Limnetis directly from some orginally marine 

 cladocerous type like the marine forms now 

 existing, such as Evadne. We imagine that 

 when a permanent body of fresh water became 

 established, as, for example, in perhaps early 

 Silurian times, the marine forms carried into 

 it in the egg-condition, possibly by birds or by 

 high winds, hatched young, which, under favor- 

 able conditions, changed into Sida, Moina, and 

 Daphuia-like forms." 



Professor Packard appears to have over- 

 looked the difficulty of the eggs of any marine 

 cladocerous t^'pe of animals surviving a sud- 

 den transfer from salt to fresh water, and the_ 

 absence of birds in the Silurian, which might 

 well deter the boldest speculator from ofl'ering 

 "such an explanation ; but when we consider that 

 permanent bodies of fresh water were undoubt- 

 edly formed by the gradual freshening of bodies 

 of salt water cut off from the ocean, and that 

 such bodies of fresh water usnally had outlets 

 connecting them with the sea, it is not surpris- 

 ing that Fritz Miiller, Dohrn, and others should 

 overlook a difficulty which is no greater for 

 Phyllopoda than for other groups of fresh- 

 water animals. 



In the chapter on his new order, Phyllocarida, 

 and its S3'stematic position, Professor Packard 

 describes the anatom}' and development of 

 Nebalia, and discusses its fossil allies. The 

 appendages of Nebalia bipes are described and 

 full}' figured, but on the internal anatomj^ very 

 little that is new is given. The figures and 

 text intended to elucidate the histology, like 

 mostof Professor Packard's similar work, leaA'e 

 much to be desired. 



The bibliography consists of a hundred and 



