piiOFESsoE iitetl's ajtatomical kotes. 101 



tlie perfectly closed spermato-genetic cells in the testicle, and this is 

 not only the case among tlie Progs, but prevails, without exception, 

 throughout the whole classes of the Eeptilia and Amphibia. 



10, Oil some additions to our Jcnoioledge of Retia mirahilia. 



I have just concluded a memoir on recently discovered " Eetia 

 mirabilia " in Mammals and Birds, which is for presentation to the 

 Imperial Academy of Science, and which will probably be published 

 in the Transactions of that learned Society. But as I cannot hope 

 that its publication will take place for some time, I give the follow- 

 ing brief epitome of its contents, but refrain from giving the descrip- 

 tive particulars in detail. In Birds these Eetia mirabilia occur 

 only in the Tibial artery (Tibio-tarsal artery) of long-legged species 

 — they are not found in any of the short-legged species — this con- 

 clusion is the result of the investigation by means of injection of 

 more than fifty genei'a. The rareness of injected preparations of birds, 

 wiU add somewhat to the value of my memoir ; one great merit of 

 which will consist in a series of splendid drawings from nature. It 

 may be of interest to append the names of some of the more remark- 

 able. Among the Cursores, I foimd the most complicated and richest 

 Uete mirabile in the Apteryx awstralis, where it extends from the 

 foreleg to the middle of the elongated tarsus ; it covers the main 

 trunk of the tibial and tarsal artery, crossing and recrossing it, so 

 that, to the casual observer, it would appear as if the artery split up 

 into so many branches, and that these composed the rete, but on closer 

 examination the tibio-tarsal artery will be seen threading its way 

 underneath the densely compact mass of the rete, and emerging, 

 undiminished in its size, from its inferior end. In the Ostrich 

 (^Struthio); Rhea ; Dromaius ; Casuarius; Leptoptilus ; Plioenicopterus ; 

 Ardea; Ibis o'eligiosa (Sacred Ibis), and many others belonging to the 

 ArdeidfB, the rete is found only in the foreleg. In the Ostrich 

 and its congeners the rete is very small, consistiug of a few (2-4) 

 elongated and very slender branches, which are so closely applied to 

 the chief trunk of the tibial artery, that their discovery and isolation 

 require a good eye and sharp instruments. In the Apteryx the 

 numerous vessels that enter to form the rete never return to unite 

 with the tibio-tarsal artery, from which they originally sprung. 

 "When they cease to surround and accompany that artery, they imite 

 to newly formed arteries, providing for the deficiency of the colla- 

 teral branches of the main artery, which latter are totally wanting 

 from the commencement of the rete. I lay some stress on the fact 

 that the main trunk of the anterior tibial* artery and its prolonga- 

 tion as tarsal is only destined to supply the toes, the rest of the soft 

 parts of the foot receive their blood from the various newly formed 

 arteries, into which the rete mirabile branches off" at its inferior 



* The posterior tibial is wanting. 



