xcii THE BEGINNINGS OF LIFE. 



changed into a Filan'a, or whether Filaria-Y\\ie worms are 

 converted into GregarincB. Leydig at first held the former 

 view, but now, in common with Henle and Bruch, he inclines 

 to the latter, since otherwise it would seem impossible to 

 account for the undoubted production of psewdo-NavicellcB 

 and PsorospermicE within GregarincB. The development of 

 the Nematoid from the Gregarina would seem to be much 

 more possible than the reverse process. And if it chanced to 

 be a kind of metamorphosis which only occasionally happened 

 (Dr. Gros), then its occurrence would be quite compatible 

 with the production of pseudo-NavicellcE in other cases. 



But whether the developmental cycle of the GregarincB is, 

 in all cases, such as has been indicated by Lieberkiihn, or 

 whether they are occasionally related to the Nematoids, it seems 

 almost certain that the peculiar bodies known as Psorospermice 

 are more or less analogous to i\\Q psaido-Navicella progeny of 

 the Gregarinidce. Professor Huxley says ^:—' The Psoro- 

 spermia are pyriform sacs, frequently provided with an 

 elongated, filiform, motionless appendage, and containing 

 two or four clear rounded bodies, attached side by side, 

 within their smaller ends, and besides these, as Lieberkiihn 

 has lately pointed out, a rounded mass of plasma. Under 

 fitting conditions the Psorosper?ma bursts, and the plasmatic 

 mass emerges as an amoebiform creature. The sacs in 

 which the PsorospermicB are developed, on the other hand, 

 can be traced back to amoebiform masses full of granules ; 

 and it seems a legitimate conclusion that the Psorospermta 

 are the pseudo-NavicellcB of an Amoebiform Gregarina, or 

 Gregarinoid Amceha' 



The naked AmoehcB are, however, closely related to Ar- 

 cellinge, which are simply Amoeba inhabiting a single- 

 chambered shell, and these again are connected by almost 

 ^ 'Med, Times,' 1856, xxxii. p. 508, 



