170 QUARTERLY CHRONICLE. 



as appears primarily in the skin, in the subcutaneous fibrous 

 mesh, or in the aponeurotic tracts, may be called " parostosis." 

 Bones which were thought to be homologous prove, when 

 examined by the light of this division of the ossifying pro- 

 cess, to be quite distinct, originating in many cases quite 

 differently ; and others supposed to be simple prove to con- 

 tain both ectosteal and parosteal elements. In the Elasmo- 

 branch Fishes Mr. Parker has studied (as also has Gegen- 

 baur) the essential cartilaginous part of the shoulder-girdle. 

 In the Ganoid and Teleostean Fishes he is able to point out 

 what membrane and dermal bones (parosteal elements) are 

 added thereto ; and thus, starting with a clear knowledge of 

 these two distinct factors, he is able, when he arrives higher 

 up in the scale, amongst reptiles, birds, and manmials, to 

 trace out the gradual fusion of the two elements, and to 

 show, in the simple-looking but often highly complex bones 

 of the shoulder-girdle which part represents this or that 

 membrane- or cartilage-bone in the fish, and what is special 

 and peculiar to the class under consideration. The magnifi- 

 cent volume, with its thirty coloured plates, which Mr. Parker 

 has produced, contains the most accurate details concerning 

 these structures, and is the result of a surprising amount of 

 research and industry. Mr. Parker's method has yet to be 

 applied fully to other parts of the skeleton, and, as he him- 

 self suggests, it is to be hoped that the present volume may 

 be looked upon as a specimen of what sound osteological 

 research should be at the present time, and that others may 

 be induced to work in the same way and with as valuable a 

 result. 



A new Rotifer. — We recently noticed Professor Mecz- 

 nikow's discovery of Apsilus lentifonnis, a Kolatorian entirely 

 destitute of vibratile cilia, and M. Claparede now communi- 

 cates an account of an animal of the same kind observed by 

 him some years ago in the Seine, a small river of the canton 

 of Geneva. It was found creeping on the bodies of Tricho- 

 drili, and other small Oligochoeta. The body of this animal, 

 to which M. Claparede gives the name of Balatro calvus) 

 is more or less vermiform, and very contractile. Its poste- 

 rior extremity (foot) is divided into two lobes, x>f which the 

 ventral is semilunar, with acute angles, which are capable 

 of invagination. The dorsal lobe forms a flattened cylinder 

 terminated by three mammilUw Between the two lobes the 

 anus is situated. The anterior extremity, which is indis- 

 tinctly annulated, is capable of retraction as in other Rota- 

 toria. The mastax is not largely developed, and is armed 

 with a very small incus, and with two curved mallei; it 



