■358 NATURAL SCIENCE. December. 



not more fully justified the title of that hodge-podge of elementary 

 science, it has made a more rational use of it by substituting 

 experiments — or, at least, the suggestion of experiments — for what 

 was originally a lecture syllabus only. It is perfectly true that 

 lecturers of any standing have for years used apparatus in illustration 

 of their remarks, but the syllabus as now drafted cannot fail to 

 re-model the whole subject. Instead of a smattering of geology and 

 astronomy with a little physics and chemistry thrown in, the students 

 will now have placed before them enough of each of these sciences to 

 whet their appetites, and to help them in making up their minds as to 

 which branch they will in future pursue as a separate subject. That 

 part of the new syllabus relating to physics (or so much of it as is 

 intended to be taught in physiography classes) has been drawn up 

 with especial care ; but to our thinking too much astronomy is still 

 apparent, whilst biology, in its relations to the distribution of animals 

 and plants, is hardly insisted on at all. How diiferent the subject as 

 now drawn up by the Science and Art Department is from that 

 originated by Huxley, must be very evident to those who have 

 followed the fortunes of " physiography" from its commencement. 



The Hinge of Bivalve Molluscs. 



On page 153 of volume viii. we referred to the researches of Dr. 

 Felix Bernard upon the hinge of Pelecypoda. A further instalment 

 of his results has appeared [Btill. Soc. Geol. France, 3^ ser., t. xxiv., 

 pp. 54-82), and gives an account of the development of the hinge in 

 the Taxodont group of that class, i.e., those with a great number of 

 teeth in a row, such as Avca and Nucula. 



Dr. Bernard points out, by way of preface, that the prodissoconch 

 stage is so similar in all the groups as to lead naturally to the 

 conclusion that it recalls a non-differentiated ancestral form ; and he 

 considers that the completed prodissoconch corresponds to a period of 

 rest in the growth of l;he animal and of its shell, during which the 

 internal organs arrive at perfection and the various cells specialise. 

 This completed, growth recommences brusquely, but always least 

 actively in the region of the hinge. 



In the Taxodonts, as in the Heterodonts and Desmodonts, Dr. 

 Bernard finds that the ligament originates in an internal central pit. 

 Along the upper margin of the hinge-line, however, there appears a 

 row of small quadrangular crenulations, which in every respect act as 

 do the teeth of the adult shell : with these last, however, they have 

 nothing to do. These prodissoconchal teeth the author has, since his 

 previous paper appeared, found in a few Heterodonts. The true teeth 

 of the adult shell arise on the hinge-plate, on either side of the 

 ligament, by the formation of shelly ridges more or less parallel to the 

 dorsal shell margin, much as they do in the Heterodonts, but arching 

 over afterwards as growth proceeds. Both sets of teeth are present in 



