Februarys, 1900.] 



SCIENCE. 



177 



red is the acid differential of the yellow 

 pigment. Acid may come from acid formed 

 by metabolism (uric acid) or secreted by 

 special cells. 



Brown, dark brown and black are due 

 to the oxidation of the yellow waxy pig- 

 ment. 



I may express the relation of these pig- 

 ments in the following diagram : 



Notes on mammalian embryology: Charles 



S. MiNOT. 



The author exhibited drawings, wood 

 engravings made in Germany, and lantern 

 slides illustrating the development of the 

 pig. The work has been done in connec- 

 tion with the preparation of an ' Introduc- 

 tion to Embryology' for the use of students, 

 intended for practical work. It is proposed 

 to study a few of the most typical stages in 

 a series of carefully selected typical sec- 

 tions, and to connect the descriptions of these 

 sections with explanations of the relations 

 of the embryonic organs to the adult anat- 

 omy on the one hand, and to the germ 

 layers on the other. The principal engrav- 

 ings are being made by Probst in Bruns- 

 wick, the author believing that the Ger- 

 man method of wood engraving is better 

 adapted to the representation of sections 

 of embryos than are either the ' process ' 

 methods, or the American style of wood 

 engraving. 



On the spermatogenesis of Peripatus : Thos. H. 



Montgomery, Jr. 



The spermatogenesis of Peripatus balfouri 

 Sedg. is interesting, first, because it has es- 

 sentially the type of that of Insects (as dis- 

 tinct from that of Crustacea as known for 

 the Copepoda), and second, because the 

 character of its cells is very favorable for 

 the determination of the stages which oc- 

 cur in the synapsis stage (an anaphase of 

 the last spermatogonia division). The re- 

 duction of the number of chromosomes 

 (from 28 to 14) takes place in the early 

 synapsis by a fasion end to end of every 

 two chromosomes, those ends of the chro- 

 mosomes joining together which are sit- 

 uated nearest that point of the cell where 

 the centrosomes lie. Each resulting biva- 

 lent chromosome has the form of a U or V, 

 whereby the bend or angle of the U or V is 

 the point of union of two univalent chro- 

 mosomes ; this point of union is effected by 

 a band of linin which appears to be a rem- 

 nant of that continuous linin spirem thread 

 present in the preceding prophase of the 

 spermatogonic division. Later the two 

 arms of each bivalent chromosome become 

 longitudinally split. The chromosomes ap- 

 pear to preserve their separateness (indi 

 viduality) during the following rest stage. 

 In the first spermatocytic division each 

 bivalent chromosome becomes transversely 

 split (through the linin band joining its two 

 component univalent chromosomes); in the 

 second spermatocytic division each (now un- 

 ivalent) chromosome becomes longitudi- 

 nally split. This account serves merely as 

 a brief preliminary note to observations 

 which will be soon published in exienso. 



Palmmonetes and salinity ; an experimental 



study in evolution: Roswell H. Johnson 



and Robert W. Hall. 



A common shrimp on our Atlantic coast, 



Palcemonetes vulgaris, is provided with small 



spines on the beak or rostrum. These 



