490 THE AMERICAN NATURALIST. | [Vor. 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), 7. 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 regards 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 Z. 
canadense of Allen’s description. Farmer and Moore intro- 
