ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 283 



c. G-eueral. 



Effect of Silicic Acid on Blastomeres and Somatic Cells.* — 

 0. .lichel calls attention to the fact that " Kieselgur " and other earths 

 have sometimes been eaten by man. He has tried to discover whether 

 the cytoplasm can dissolve siliceous skeletons. He produced giant-cell 

 tumours in the peritoneum of guinea-pigs by injecting Kieselgur, and 

 found that there was eventually a complete disappearance of the silica. 

 The same power of dissolving flint is well seen in the blastomeres of the 

 fro2:'s eo^g-. 



The silica of a diatom shell or the like is dissolved. This occurs 

 only in the internal cytoplasm. The formation of giant-cell tumours 

 is an adaptive reaction for dealing with the siliceous bodies. 



Amphibian Tonsil s.f — B. F. Kintrsbury finds that structures hav- 

 ing the histological characteristics of tonsils occur in connexion with 

 the oral (pharyngeal) epithelium in Amphibia. Thus in Salamandra 

 atra they occur in some twelve places. While they exhibit considerable 

 variability in occurrence and location, they are definite and constant 

 enough in four regions to warrant the application of local names — 

 choanal, lateral, sublingual, and preglottideal tonsils. 



In structure these tonsils show the following characteristics : {a) 

 an accumulation of round cells beneath and within the epithelium ; 

 ih) thickening of the epithelium ; and (c) intimate relations to the 

 blood-vessels. Mitotic figures occur in the tonsils, and there is evi- 

 dence that they are centres for lymphocyte formation. 



In other Amphibia, sublingual and lateral tonsils occur in Desmogna- 

 thus fnsca, sublinguals in Amhlyf<toma jninctatum, laterals in DiemyctyJus 

 and Phetlwdon, sublinguals in Bufo lenfiyinosus. Xone were found in a 

 specimen of Gyrinophilus porphyriticus. 



The sublingual, lateral, and preglottideal tonsils of Salamandra atra 

 occur at sites which in the metamorphosis are marked by absorption, 

 particularly or more evidently of epithelium. The amphibian tonsils 

 appear to develop relatively late and slowly, after the completion of 

 metamorphosis. Their homology with other tonsils is doubtful. The 

 " Kiemenreste " of Maurer (glandul^e pseudothyroide^) and the tonsils 

 are l:»elieved to belong to the same category of organs. 



Eyes of Periophthalmus and Boleophthalmus.| — L. Baumeister 

 gives an account of the structure of the eyes in these two fishes, which 

 are well known to spend hours on end out of water on the mud of 

 tropical estuaries. He differs in many points from Yolz. What Volz 

 calls the cornea is only the superficial part, the conjunctival part ; the 

 so-called retractors of the cornea are not muscles but connective- tissue ; 

 an infolding of the conjunctival part of the cornea is physically 

 impossible. The structure in front of the lens w^hich Yolz interprets 

 as the transparent terminal sinew of the scleral muscle corresponds to 

 the substantia propria (Beer) of the cornea. The cavity between the 



* Anat. Anzeig., xliii. (1913) pp. 212 20. 



t Anat. Anzeig., xlii. (1912) pp. 593-612. 



X Zool. Jahrb., xxxv. (1913) pp. 341-54 (6 figs.). 



