1 1 6 E VOL UTION AND DISEASE. 



scope and cataract needle dividing them into two, three, 

 or four pieces. Detailed accounts of six experiments 

 are given in which the ova were simply divided, cut into 

 three portions, or quartered. The results of these experi- 

 ments were as follows : 



1. Development continued in the divided pieces. 



2. The smaller the piece the slower the growth of the 

 larva. 



3. The smaller pieces tended to form incomplete 

 individuals and inclined towards monstrosity. 



These observations are valuable, for it must be borne 

 in mind that the growth of a morula (segmented ovum), 

 after artificial division, differs very much from the forma- 

 tion of a hydra out of a piece cut from an adult hydra. 



From Syphonophora we may pass to worms. In 1828 

 Dug^s 1 presented to the Academic Royale des Sciences, a 

 paper entitled, " Recherches sur la Circulation, la Respira- 

 tion et la Reproduction des Annelides a Branches," 

 which contains the following remarks relative to the eggs 

 of the worm Lumbricus trapezoides ; 



" The first of these eggs which I opened embarrassed 

 me much. I saw escape with a glairy material a living, 

 white, soft, transversely wrinkled, vermiform animal, 

 composed of a body terminated by two appendages 

 marked from right to left by a regular spiral. It was a 

 monster formed of two individuals joined together, fused 

 in a part of their length, as I have since observed in 

 others but with less symmetrical conformation. In each 

 egg I have constantly found plunged in the same 

 albuminous jelly, either two germs, two cicatricula, or 

 1 " Annales des Sciences Naturelies," tome xv. p. 248. 



