330 SYNOPTIC COLLECTION. 



Bernard 1 maintains that this large number of segments 

 is one of many proofs that the Apodidae, and with them 

 all the Crustacea, have arisen from carnivorous worms. 

 He takes great pains to bring out the resemblances of 

 Apus to a carnivorous worm, but in doing this he is deal- 

 ing with adults, and is attempting to connect the mature 

 forms of one subkingdom with those of another. 



On the other hand, Packard 2 considers the excessive 

 number of segments in Apus and the irrelative repetition 

 of abdominal feet as signs of a vegetative repetition of 

 parts in a type which has culminated and is subject to 

 decline and extinction. He finds that the Phyllopods as 

 a whole, especially the Apodidae and Branchipodidae, 

 are a comparatively recent, extremely specialized group 

 which was developed under exceptional biological condi- 

 tions in salt lakes or in bodies of fresh water. He also 

 points out the important fact that although fossils of 

 Phyllopods are found in the Palaeozoic rocks, they appear 

 to have been fresh-water forms, since their remains occur 

 in fresh-water strata. 3 



The eyes of Apus are prominent. Extending from the 

 ventral side are the two pairs of long, slender antennae. 

 Back of these are the mouth parts and swimming-feet 

 (No. 811). 



One of the modified Phyllopod crustaceans is Estheria 

 californica Pack. (No. 812). No one could imagine at 

 first sight that this animal was in any way related to a 

 Gammarus, lobster, or crab. The fleshy organs are cov- 

 ered by a bivalve shell (PI. 813, fig. i, enlarged; the line 

 shows true length of shell) which is provided with a 

 hinge, with small umbones placed near the anterior end, 

 and with what appear to be distinct lines of growth. 



1 The Apodidae, 1892, p. 18 (Nature series). 



2 1 2th Ann. Rep. U. S. Geol. and Geogr. Surv., 1878, part i, 

 p. 418. 



3 Loc. cit., p. 419. 



