230 THE MICROGRAPHIC DICTIONARY. 



important discovery of the seat and nature of the ciliary 

 action so manifest in that sponge. The notice of Sponge, 

 again, is very imperfect, and in the description of the figures 

 the bases of the sponge spicules are termed the apices, and 

 vice versa. In the Acalephge the arms, tentacles, &c,, are 

 stated to be covered with cilia, and the class generally is said, 

 without any hesitation, to be furnished with a distinct nervous 

 system, and with blood-vessels containing coloured blood, 

 distinct from the chylaqueous channels, although under the 

 head of " chylaqueous system," Dr. Williams's assertion is 

 adopted, that a separate blood vascular system is not found in 

 any form, even in the most rudimentary, below the Echinoder- 

 mata, and the Acalephm are particularly noticed as not pos- 

 sessing one. The omissions, however, in this department of 

 the dictionary are of still greater importance. We look in vain 

 for the words Bryozoa or Polyzoa^ a class of animals wholly 

 microscopic, and containing forms of the greatest variety, 

 beauty, and interest, abounding in the sea and in fresh waters, 

 and together with the equally neglected Sertulariadans, the 

 constant objects of never-ending, pleasing observation to the 

 young and old microscopist. 



If half the botanical articles (in number) had been omitted, 

 and many of those relating to the animal kingdom, including 

 nearly all those on human histology, which are quite out of 

 place in the micrographical dictionary, room would have been 

 afforded and to spare for matters such as the above, and 

 numerous others, of far greater interest and value to the large 

 class of general readers, for whom such works as the Micro- 

 graphic Dictionary are specially intended. 



Having thus shown what we regard as the defects in the 

 Micrographic Dictionary, the more pleasing and longer task 

 would remain had we space to indicate its merits. As we 

 have said, the great bulk of the articles are valuable and well 

 selected, and it is impossible to commend in too high terms 

 the way in which the book is " got up." It is enough, perhaps, 

 to say that it is worthy of the publisher, printer, and artist. 

 The illustrations are copious, clear, and well selected, and 

 alone would confer great value upon the work, which we 

 strongly recommend to all who may require a compendious 

 summary of what is known on a vast variety of interesting 

 microscopic objects, and assistance in the mode of pursuing 

 microscopic researches. 



