xxvi SCIENCE PROGRESS. 



trations, especially of anatomical points bearing upon the classification 

 of the orders. For example, we find Burger's classification of the 

 Nemerteans adopted, which, as is well known, is largely based upon 

 the relations of the nervous system to the muscular layers of the body 

 wall, but not a single figure is given in illustration of this important 

 point. 



Prof. Sedgwick justly lays great importance upon the presence of a 

 true coelom, but there are certain disadvantages in the present state of 

 our knowledge attending the adoption of the ccelomata as a group of the 

 Metazoa, for it causes a complete and wide separation of the Rotifera 

 from the Annelida, whereas judging from the striking structural resem- 

 blance of certain of the former with the trochosphere larva of the latter 

 group, one would have been inclined to place them close together, and 

 when we remember that the development of the sexually produced 

 embryo of the Rotifera is still unknown, and consequently also the true 

 origin of its body cavity, it seems somewhat premature to so widely 

 separate these two groups. The fact that in the adult Rotifera and 

 Nematoda neither the excretory nor the generative organs appear to be 

 connected with the body cavity, does not entirely preclude the possi- 

 bility of the latter being a true ccelom, therefore it appears to us 

 that Prof. Sedgwick's adoption of the group coelomata, however pro- 

 phetic it may be, is nevertheless distinctly premature and inadvisable in 

 a student's text-book. 



We do not think that the majority of molluscan specialists will 

 agree with our author in his severance of the Chitons from the Soleno- 

 gastres, and to state that such an association was " quite unjustifiable " 

 and of the latter that " they are not Gasteropoda," when we consider 

 the eminent malacologists who have grouped them together, appears 

 to us to be hardly supported by sufficient evidence, and Prof. Sedgwick 

 goes further and throws out a suggestion that the Solenogastres may 

 not be mollusca at all. The main reason given being that the gonads 

 in the Solenogastres open directly into the pericardium, but, as Prof. 

 Sedgwick points out in other parts of this book, the latter is only 

 part of the coelom in connection with which the gonads are invariably 

 developed, and with which the perigonadial cavity communicates through 

 the kidney (another part of the coelom) in Fissurella, Haliotis, some 

 Lamellibranchs and more directly in the Cephalopoda, and when we 

 consider the similarity of the nervous system of the Solenogastres with 

 that of Chiton, the condition of the foot in Cryptochiton and that of 

 the organ believed to be its homologue in Neomenia, and the many other 

 points of resemblance, I think the majority of us would conclude that 

 the group Amphineura was a natural one, and that at all events the 

 Solenogastres were mollusca, and found their nearest relatives in the 

 Polyplacophora. A few more anatomical illustrations might well have 

 been accorded to this group, and a reference given to Simroth's fine work 

 on these forms in Bronn's Thierreich., Bd. 3., Abth. 1. 



The molluscan part of this work is by no means the most satis 



