Relation between Nucleolus and Chromosomes. 53 



of the contrary opinion. Carnoy and Lebrun (1897-1899) state their con- 

 clusion concerning amphibia that the chromosomes are derived from the 

 nucleoli. Their figures are very convincing on this point. Macallum (1891) 

 believes that the chromosomes have a double origin in amphibia. Jordan 

 (1893), basing his opinion on observations made on the ova of the newt, 

 believes that the nucleolar particles do not contribute to the formation of the 

 chromosomes. Lubosch (1902), in the case of the ova of Triton, states: 

 " Es ist sicher, dass die in diesen Stadium (maturation) vorkommeden 

 Chromosomen zum Theil nukleolaren Ursprung haben ' : (p. 250), thus 

 agreeing substantially with Schultze. 



Holl (1893), investigating the ovum of the mouse, finds that the central 

 granules of the nucleolus wander out and so become chromosomes. Sobotta 

 (1895), on the other hand, holds that the chromosomes are not derived from 

 the nucleoli only, but from the whole chromatic substance of the nucleus. 



According to K. Foote and E. E. Strobel (1905), the chromosomes of 

 the first maturation spindle in the annelid AllobopJwra jcetida, " are formed 

 by a gradual segregation of the chromatin, which is dispersed through the 

 germinal vesicle," the nucleolus meanwhile persisting in its original form 

 and size. The chromosomes are thus not formed at the expense of the 

 nucleolus. Similar conclusions were reached by Korschelt (1895) in the 

 case of the annelid Ophryotrocha, and by Wheeler (1897) for Mysostoma, 

 and by Griffin (1899) for Thalassema. There seems to be almost complete 

 agreement among investigators that in annelids the chromosomes are not 

 derived from the nucleolus. Coe (1899) inclines to this opinion also in 

 the case of Cerebratulus, as also Gathy (1900) for Tubife.v and Van Beneden 

 (1883) for Ascaris megalocephala. However, in the case of Chcetopterus, 

 according to the figures of F. Lillie (1906), the chromosomes find at least 

 a partial source of origin in the nucleolus; also Vejdovsky (1888), who 

 studied the ova of Rhynchelmis, and Blockman (1882), who investigated 

 Ncritina, incline to a nucleolar origin of the chromosomes. Both Halkin 

 (1901) and Goldschmidt (1902), as a result of their study of the ova of the 

 trematode Polystomum integer rimum, hold that the chromosomes are derived 

 exclusively from the nucleolus. 



Results of recent observations on echinoderm eggs point to at least a par- 

 tial nucleolar origin of the chromosomes in the various forms. R. Hertwig 

 (1896) studied the unfecundated eggs of the sea-urchin and the starfish 

 poisoned with strychnine. He states that the nucleolus vanishes within the 

 nucleus as the chromosomes appear, and he holds the opinion that the 

 chromosomes receive a portion of their substance ; ' notwendigerErganzungs 

 material" -from the disappearing nucleolus. E. B. Wilson (1901) finds 

 two widely different types of chromosome formation in the eggs of the 

 sea-urchin (To.vopneustcs rariegatus) artificially fertilized by Loeb's mag- 

 nesium chloride method. The two types, however, did not coexist in the 



4* 



