39§ NOTES AND COMMENTS [December 1899 



of the past in man's present structure, he impressed us with the idea 

 that we carry about with us a museum of relics, that some of our 

 structures are at present in a transition-stage of function-change, and 

 that some parts are even progressing. 



In a recent essay, entitled " Senescenza filogenetica " (Rivista di 

 Scienze Biol. 1899, Fasc. iv. pp. 1-7), he has pointed out (1) that 

 organs in process of phylogenetic regression, e.g. the tips of the lungs, 

 the caudal end of the spinal cord, Morgagni's pouches in the larynx, 

 and the posterior molars, have their weak spots, their loci minoris 

 resistentiae, where they are peculiarly disposed to disease ; (2) that 

 organs and parts of organs in process of function-change, e.g. the 

 thyroid, the thymus, the inferior nasal muscles, and perhaps the 

 tonsils, are likewise peculiarly open to attack ; and (3) that progressive 

 parts, such as certain muscles and bones, are strong in their progress- 

 iveness, and less liable to disease than the parts in the two preceding- 

 categories. One cannot help wondering with another reviewer, Dr. 

 W. A. Nagel, whether the last statement will hold good in regard to 

 our brains, which we fondly hope are also on the line of progress. c 



There appear to be two distinct ways of interpreting this 

 " phylogenetic senescence." On the one hand, we have to consider the 

 immediate physiological conditions, e.g. of diminished blood-supply 

 and weakened innervation, which may lessen the resisting power of a 

 dwindling organ. On the other hand, we have, with Weismann, to 

 go further back, and consider the possibility of a germinal struggle and 

 selection among the stronger and weaker determinants, and supple- 

 mentary to both interpretations there is the normal action of natural 

 selection. 



Studies in Plant Morphology. 



Schumann of Berlin has recently published through Engelmann 

 (Leipzig) a second part (pp. 207-313) of his " Morphologische Studien." 

 The studies are of a special and somewhat abstruse character, dealing 

 with flower- and leaf-arrangement and including questions of develop- 

 ment, mechanical conditions and the like. They will be read with 

 interest by the somewhat limited number of botanists who can 

 appreciate or follow such discussions. The first (No. III.) deals with 

 the vexed question of the peculiar inflorescence in the Boraginaceae 

 and Solanaceae, and is a criticism of a publication by Kolkwitz. The 

 second (No. IV.) is an account of the branch- and floral-development 

 in a commonly grown greenhouse plant, Scirpus setaceus (Isolepis 

 setacea). No. V. deals with the leaf-arrangement in screw-pines, while 

 No. VI., occupying two-thirds of the whole part, and entitled "The 

 Shifting of Organs on Growing Shoots," is mainly a criticism of 

 Schwendener's views on the same subject. 



