Bibliographical Notices. 373 



Kolk has overlooked this remarkable structure, and supposes the 

 tracheae to end blindly, simply attached by their ends to the inner 

 surface of the skin. According to him, the air in the respiratory 

 organs is renewed through an opening in the middle of a horny plate 

 closing the great aeriferous cavity, at the posterior extremity of the 

 body from behind. Schroedcr van der Kolk even assumes the exist- 

 ence of a sphincter around this supposed opening. Mr. Meincrt 

 shows that this is a mistake : in the place of the supposed perfora- 

 tion there is merely a pellucid spot, and an impression on the horny 

 plate, caused by the existence in young larvse of a small gland on 

 this spot, which is obliterated in the adult larvae. A communication 

 between the air enclosed in the aeriferous chamber and the outer air, 

 through the horny plate closing it from behind, is possible only in so 

 far as it is permitted by the structure of the said plate itself, which 

 consists of a not very close texture of chitinous filaments, externally 

 covered by a firm but thin membrane. When this plate is viewed 

 from behind, it presents six slits of a curved shape, forming concen- 

 trical lines, three on each side of the pellucid point in the middle. 

 Each of these slits opens directly into a double row of vesicles con- 

 taining air. Schroeder van der Kolk supposed these slits to be closed 

 by a very thin membrane, the whole structure representing a kind of 

 trachea-gills ; but Mr. Meinert has shown that they are perfectly 

 open, the air being detained in them by their margins being finely 

 denticulated. The number of these slits varies according to the age 

 of the larvae. 



According to Schroeder van der Kolk, the alimentary tube is con- 

 nected with the adipose tissue in such a maimer that the nutritious fluid 

 may directly flow from one into the other. Mr. Meinert shows that the 

 foremost set of connecting tubes, according to Schroeder van der Kolk, 

 are in reality mere ligaments, and that, as regards the second set of 

 such tubes assumed by Schroeder van der Kolk, this anatomist has 

 been misled by the circumstance that the longer pair of the Malpi- 

 ghian vessels, in the larva of Gastrus Equi, as well as in many other 

 insects, presents a different structure in their anterior and their pos- 

 terior parts. Their extreme ends are, as usual, fixed to the posterior 

 parts of the intestine, but do not, as Schroeder van der Kolk thought, 

 open into it ; and although the said vessels are fixed to the adipose 

 tissue at that point where their two different structures meet, there 

 is no communication between their cavity and the adipose vesicles. 

 "With respect to the dorsal vessel, Schroeder van der Kolk has also fallen 

 into a serious mistake, namely, in considering certain lateral ligaments, 

 which keep the vessel in its place, as a kind of aortas. Although 

 Mr. Meinert has thus divested Schroeder van der Kolk's treatise of 

 much that appeared as its most striking results, there is so much left 

 to admire in it that naturalists will not be justified in disregarding it 

 for the future, as has hitherto been the case. 



The aim of Mr. Didrichsen's paper, to which we would next direct 

 attention, is to correct certain mistakes concerning the nature of the 

 thorns in Berberis, Ribcs, and Parkinsonia, which seem in a great 

 measure to pervade botanical literature ; and also to free the great 



