INVERTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 449 



meshwork, and there is a network of interspaces; no signs of any 

 network can be seen in the teeth, for these have for their constituent 

 elements lamellfe, or scales and prisms ; the former are chiefly found 

 in the body of the tooth, and the latter in the carina or longitudinal 

 ridge, the face of which is directed towards the enteric tract. 



The details of the paper are beyond the limits of any abstract, 

 but their careful study leads the author to some not uninteresting 

 conclusions. He has been led to see that Haeckel was justified in point- 

 ing out that, although the sensory organs of these creatures are but 

 very feebly developed, the complicated structure of their hard parts is 

 sufficient to justify their having a somewhat higher place in a zoo- 

 logical classification than is usually assigned to them ; at the same 

 time the author reminds his readers that the Ehizoj)oda also exhibit a 

 considerably complicated structure of their test. 



The writer does not point out the bearing which results of this 

 kind have on the doctrine of evolution ; it will however naturally 

 suggest itself that the necessary conditions of existence having been 

 in each case complied with, the animal has devoted itself to the com- 

 plication of its parts in much the same way as a society of human 

 beings at peace becomes daily more complex from the special activity 

 of its individual members. 



The tooth is attached to a saccular membrane which appears to bo 

 an invagination of the buccal membrane ; in this membrane there is 

 no ajjjjcarance of cell-boundaries, but there are in it structures 

 resembling the nuclei of cells ; from it processes are given off which 

 extend through the whole tooth, and surround all the calcareous 

 parts. The presence of such protoplasmic parts is not only spoken 

 to by the mode of growth of the teeth, but also by the fact that there 

 are to be seen, in the larger lacunae, bodies which are very much like 

 cell-nuclei. The tooth would, in fact, appear to be thus developed : 

 the epidennis of the animal extends inwards, the scales begin to be 

 develoj)ed, the interspaces remain filled with living sarcode, and this 

 finally forms a network, in the interspaces of which we find the 

 skeletal parts. When the disks are developed this sarcode begins to 

 disappear, and that only remains which has been already noticed. 



Like other hard parts, of no a2)2)arcut importance at first sight, 

 the form of the skeletal parts of the tooth, and es])ecially of tho 

 scales, apj^ears to be constant in different genera, and, so far as 

 observati(tn extends, in different species; the author goes so far as to 

 say tluit tlie form of the i)arts so afi'ects the contours of the wliolo 

 tooth, tliat a drawing of the circumference of a transverse section is 

 probably sufficient to determine the species, and certainly the genus. 

 If this be tho case, Gicsbrccht's observations will bo of some assist- 

 ance to systematists. 



New Organ of the Cidaridae.* — The structure described under 



this name by Dr. Hubert Ludwig is no other than that to which 



Mr. C. (Stewart has already directed attention ; j it is, however, of 



interest to observe tliat the German investigator has found, us Mr. 



* '/cit-olir. wih.s. Z>K)1.,' xxxiv. (ISJSd) p. S2. 



t ijec' this Join Mill, li. (IST'J) i>. ^;.^!S. 



