342 ABSTRACTS OF PAPERS. [VOL. II 



7. In any one group, as the Teleosts, the apparatus has its 

 highest development in those species which are most active. 



8. The corpora quadrigemina of higher vertebrates are con- 

 cerned only with reflex functions ; therefore this apparatus 

 must have a reflex function. 



Such a short circuit avoiding the loss of time in passing 

 through a chain of neurones must be of great importance in 

 saving time, amounting perhaps to a considerable fraction of 

 a second. An animal suddenly presented with some optical 

 evidence of danger from which it recoils in fear, does so reflexly, 

 calling into use this apparatus. When we consider that in the 

 struggle for existence the saving of a fraction of a second is 

 often a matter of life or death, it becomes evident that this 

 apparatus has played an important part in the survival of the 

 fittest, and in the whole evolutionary process throughout the 

 vertebrate series. 



XII. THE SIGNIFICANCE OF THE SYNAPSIS 

 STAGE OF THE GERM CELLS. 



THOS. H. MONTGOMERY, JR. 



IN the germinal cycle of the Mctazoa may be distinguished 

 in succession the following main stages : the conjugation of the 

 maternal and paternal cells (fertilization), a number of genera- 

 tions of ovogonia (or spermatogonia), then the growth period, 

 and finally the stage of the two maturation divisions. The 

 reduction in the number of the chromosomes, i.e., the formation 

 of bivalent chromosomes, is not effected by either of the mat- 

 uration mitoses, but during that portion of the growth period 

 known as the synapsis stage. The bivalent chromosomes are 

 formed by a union, end to end, of every two univalent chro- 

 mosomes, as I have shown in a paper on the spermatogenesis 

 of Pcripatus, just published, and in another on the spermato- 

 genesis of the Hcmiptcra, now in press. 



Heretofore no one has shown exactly how the bivalent chro- 

 mosomes are produced, and no one has given any adequate 



