312 NATURAL SCIENCE. 



JUNE, 



The Apodid.^e ; a Morphological Study. By H. M. Bernard. 8vo. Pp.316. London: 

 Macmillan & Co., 1892. Price 7s. 6d. 



We cannot altogether congratulate the publishers upon the latest 

 volume of the " Nature Series." The writer has set himself the 

 " ambitious task " of proving that Apus and its immediate allies can 

 be derived from a " bent carnivorous Annelid." It is the general 

 opinion of naturalists that these Crustaceans stand nearer to tlie 

 base of the Crustacean series than any other forms. There is, 

 therefore, nothing particularly new in Mr. Bernard's contention ; nor 

 is there much evidence in the work before us added to what is 

 already known concerning this possible origin of the Phyllopod 

 Crustaceans. An ideally intermediate form between the Annelids 

 and the Crustaceans should show that essential Annelid feature — a 

 metamerism of the internal organs ; and Apus is in this respect not 

 in the least more worm-like than other Crustaceans. It is true that 

 Mr, Bernard cannot be blamed for this ; but he attempts to show 

 that Apus does show traces of this internal metamerism in the sexual 

 organs. The gonads are figured as being of an elongated form, with 

 crenations along the margin ; but it is putting too great a strain upon 

 this comparatively unimportant fact to adduce it as evidence of a 

 fusion between a series of segmentally repeated gonads. Zaddach 

 described the gonads of this animal as forming a kind of network, 

 while Mr. Bernard did not observe this, though believing, neverthe- 

 less, that it may exist ; and this fact, if definitely proved, would be 

 unquestionably of interest, for Dr. Benham, in an important paper upon 

 the testis of the King Crab [Limulus), particularly dwelt upon the 

 similarity which the retiform condition of that organ in Limnlus 

 shows to the Arachnids. As Mr. Bernard believes that Apus and 

 Limulus are not far apart, it is surprising that he has not seized upon 

 this point. 



The principal new facts in the book concern the " water sacs" 

 and the " neck gland." The former are paired sacs that spread out 

 over the eyes, and appear to contain a watery fluid during life. Mr. 

 Bernard thinks that they are an indication of the backward movement 

 of the eyes. They represent, he believes, the soft non-calcified 

 integument which lies between the dorsal sclerites. As tlie author is 

 so eager to show affinities between Apus and worms, he might have 

 made use of these structures as an argument by pointing out their 

 possible identity with the ciliated tubes of the Gephyreans and of 

 other Annelids which are related to the central nervous system. The 

 neck-gland is considered by Mr. Bernard to be an excretory organ ; 

 and it is quite possible that he is right, though here again he has 

 omitted to cite what might have been of use in assisting him to prove 

 one of his views. 



A special chapter of the book is devoted to a consideration of the 

 resemblances sliown by Apus to the extinct Trilobites. In many 

 Trilobites, at any rate, there is a pair of pores upon the head-shield, 

 which are very possil)ly comparable to these organs in Apus. Dr. 

 Henry Woodward has lately, in the Palaeontographical Society's 

 memoir on the Carboniferous Trilobites, particularly emphasised the 

 existence of these pores as evidence of a likeness between the Trilo- 

 bites and certain Isopod Crustaceans, especially Serolis, where they 

 also exist. There is probably something of interest here, though at 

 present details are wanting. 



The alleged hermaphrodite condition of Apus is the last remaining 

 matter of special interest in the volume ; and we do not think that 



