62 LECTURE IV. 



frame, seems unable to direct the metamorphosis of the primitive cells 

 along the right road to the tissues they were destined to form, but 

 causes them to retain, as it were, their embryo condition, and to 

 grow by the imbibition of the surrounding fluid, and thus become the 

 means of injuriously aifecting or destroying the tissues which they 

 should have supported and repaired. I regard the different acepha- 

 locysts, therefore, as merely so many forms or species of morbid or 

 dropsical cells. 



The conclusion to which' the known phenomena of the parasitic 

 o-regarinae lead is a different one ; and to this much-mooted question 

 I next pass. 



In 1826, M. Leon Dufour* described and figured some minute 

 entozooids, of very simple form and structure, which he discovered in 

 the alimentary canal of several species of Coleoptera. 



Subsequently, detecting them in great abundance in the chylific 

 stomach of the earwig in the month of August, the same distinguished 

 entomologist communicated a particular description of them to the 

 'Annales des Sciences Naturelles," 1828 f, proposing the name 

 Gregarina for the genus ; and he gives three figures of the species, 

 under the name of Gregainna ovalis. It is half a line in length. 

 One individual is characterised as having a spherical anterior seg- 

 ment. In a second this appears to have been lost, and is said to be 

 replaced by a sort of skull-cap (calotte). The third, besides the 

 constriction defining the anterior sphere, shows another constriction 

 equally bisecting the trunk. Of this latter specimen Dufour re- 

 marks : — " Deux individus fixes bout a bout ou tete a queue, peut- 

 etre accouples:" — but either in the act of conjugation or of sponta- 

 neous fission. M. Dufour could detect nothing in the interior of 

 these parasites except " des corpuscules arrondies," They were ob- 

 served to vomit these " corpuscles " by the anterior end (probably 

 after the fission). 



Siebold, in 1837, not succeeding in observing any signs of volun- 

 tary movement in the Gregarina, rejected them at first from the 

 kingdom of completely-formed animals, and supposed them to be eggs 

 of insects. \ Returning to the investigation, he soon, however, re- 

 nounced his first opinion, and retained the genus, as unique and 

 exceptional in its nature amongst the Entozoa. He observed, in 

 some, a feeble contraction of the body, producing a vermiform figure. 

 They consist of a very firm, smooth, completely-closed skin, which is 

 highly elastic, and includes a milk-white, minutely granular mass, 

 imbedded in which there is a clear cell, including smaller cells. 



* LIV. p. 44. t Xm. p. 366. % LV. p. 56. 



