490 THE AMERICAN NATURALIST. [Vol. XXXIX. 



Rosenberg (: 05) has recently published a general review of 

 reduction phenomena based on studies upon Listera, Tanecetum, 

 Drosera, and Arum, taking a position in essential agreement with 

 Allen and the investigators of the Carnoy Institute and in 

 opposition to the theory of Farmer and Moore and Strasburger. 

 Rosenberg does not quote Allen's preliminary paper (: 04) which 

 anticipates his conclusions. He finds that the spirem which 

 emerges from synapsis is preceded by a condition when the 

 structure is clearly made up of two threads (spirems) which lie 

 parallel to one another. These two threads are frequently 

 joined together, and in places spirally twisted but here and there 

 they may be seen to be entirely separated from one another. 

 They finally form the single spirem which follows synapsis and 

 which divides into the reduced number of chromatic segments. 

 But the chromatic segments throughout the entire processes are 

 shown to be double in structure (bivalent chromosomes), i. e., 

 composed of two chromosomes lying very close together side by 

 side or even united. What appears to be a longitudinal fission 

 of the chromatic segments of the spirem immediately preceding 

 the first mitosis is really then a line of union along which the 

 two independent threads have come together. The phenomenon 

 of synapsis consists of this close association of two threads 

 which are themselves simple spirems into a double spirem which 

 segments into pairs of sporophytic chromosomes each of which 

 may be regarded as a bivalent chromosome. 



Farmer and Moore published a preliminary communication in 

 1903 which aroused much interest in their theory of chromo- 

 some reduction. The full account (: 05) has recently appeared. 

 Their studies are upon Lilium, Osmunda, Psilotum, Aneura, 

 and the cockroach, Periplaneta. Lilium and Osmunda among 

 the plants were given chief attention and since the lily was 

 the type studied by Allen it will serve best to contrast the 

 conclusions of these two investigators. The accounts of Allen 

 and Farmer are so fundamentally different as regai^ds the events 

 of synapsis and the prophase of the heterotypic mitosis that 

 it seems scarcely possible that both can be right in their 

 respective material, Lilium candidum, Farmer's type, and L. 

 cana dense of Allen's description. Farmer and Moore intro- 



