PHAGOCYTOSIS 421 



This tissue, adds Kowalevsky, entirely differs from cenocytes, or from the so- 

 called glandular body whose formation in Gryllotalpa has been described by 

 Korotaiev, and in Bombyx mori by Tichomiroff. In a recent work wherein has 

 been collected everything known regarding these last-named cells, Pe"karsky 

 proves that they are unique in nature and cannot be regarded either as fat-cells, 

 or as pericardial cells, or even as formative leucocytes. 



t 



As to the structure of the pericardial cells, Kowalevsky adds that 



they are always attached to muscular fibres passing off from the 

 heart, and that they lie, so to speak, upon them. In the locusts the 

 muscular fibres supporting the pericardial cells appear distinctly 

 like little staves or sticks. The attachment of the pericardial cells 

 to the muscular fibres has been observed by Cuenot and reproduced 

 by him in his work, but his description somewhat differs from that 

 observed by Kowalevsky in the locust (Acrydium migrator him). 



As to the nature of the acid excretions which are formed in the pericardial 

 cells, in spite of his attempts to solve the problem, Kowalevsky has been unsuc- 

 cessful. The only observations in this direction are those of Letellier on the 

 pericardial glands of lamellibranch molluscs, which he found to contain hypo- 

 uric acid, and it is probable, says Kowalevsky, that the acidity of the pericardial 

 cells in insects is due to the presence of the same acid. 



Leucocytes or phagocytes in connection with the pericardial cells. 



It is thought by Schaffer that the leucocytes or phagocytes may 

 be free or wandering fat-body cells. They play an important part 

 in metamorphosis, while they absorb or feed upon the remains of 

 the larval organs, and thus prove of use in the building up of the 

 organs of the adult insects. 



While the faculty of phagocytosis is wanting in the urinary tubes, 

 Balbiani and more recently Cuenot have expressed the opinion that 

 the pericardial cells of insects may have the power of absorbing 

 hard bodies, " acting as a phagocytic gland." This, however, is 

 called in question by Kowalevsky, from studies made on different 

 insects. On introducing powdered carmine into the body of an in- 

 sect it has not been absorbed by the pericardial cells, as they have 

 not been colored red. It is the leucocytes which absorb the grains 

 of carmine, and which, after having dissolved them, transmit them 

 to the pericardial cells. Hence, then, the pericardial cells have not 

 the phagocytic power of which Cuenot speaks. 



Returning to his own observations on hard bodies introduced into 

 insects, or large globules introduced under the form of a milk emul- 

 sion, Kowalevsky has found that these bodies were absorbed in the 

 first place by the free-swimming leucocytes, and in the second place 

 by whole groups or nests of leucocytes situated in different parts 



