SECTIONAL TRANSACTIONS.— D. 339 



The fact that the body of the Enteropneusta is divided up into three consecutive 

 parts, the proboscis, the collar, and the trunk, each with an unpaired or paired coelomic 

 cavity, is in itself not sufficient evidence for regarding them as segmented animals. 

 There are, however, certain organs that may indicate an ancestral metamerism, or 

 they may merely represent an incipient segmentation. Of these organs the gills are 

 most important. They form a continuous and regular series in the frontal part of the 

 trunk. The gills alone, however, are not sufficient proof of metamerism. Other 

 organs, independent of the gills, should also show a metameric arrangement, corre- 

 sponding to that of the gills. The liver saccules are also arranged in a more or less 

 regular series, but they are of no value in this connection, as the liver region lies some 

 considerable distance behind the gill region. The annular depressions and thickenings 

 of the skin show a somewhat regular arrangement upon casual observation, but on 

 closer examination it becomes evident that they too do not prove the existence of a 

 possible metamerism. The only organs, other than the gUls, that are of importance 

 in this respect are the gonads. 



WiUey was unable to bring forward any fact in support of his theory, which was 

 therefore only a supposition. Some years ago Meek described an Enteropneust, 

 Olossohalanus marginatus, in which he found indications that the arrangement of the 

 gonads coincided with that of the gills. I was fortunate enough to collect a species of 

 Dolichoglossus, D. caraibicus, in which the gonads without exception alternate with 

 the gill-slits. As there are over 60 gill-slits and the first gonad lies between the 

 fourth and fifth gills, the genital and branchial region largely coincide in this species, 

 which therefore definitely supports Willey's theory. The small Dolichoglossus ota- 

 goensis has only about ten gills. Nevertheless, in this species also an alternation of 

 gills and gonads can be demonstrated and, furthermore, it gives an indication of the 

 way in which the metameric arrangement of the gonads of other Enteropneusta may 

 have been lost. 



This regular alternation of two different organs proves that the Enteropneusta 

 are related to the segmented animals. Moreover, the fact that an alteration of gonads 

 and gills similar to that of these species of Dolichoglossus occurs in the young 

 Amphioxus gives further support to Bateson's opinion that the Enteropneusta are 

 closely related to the Chordata. 



Thursday, August 1. 



Mr. Paul Selby. — South African Big Game in the Kruger National Park. 



Mr. D. R. R. Burt. — A Case of Intersexuality in Bos indicus. 



Prof. J. Versluys. — On the Chalksacs in the Anura, with remarks on their 

 probable Function. 



It is well known that Ln the frog we find on both sides of the backbone, closely 

 adpressed to the spinal ganglia, chalk sacs filled with a milky substance, identical with 

 the otoconia of the ear-labyrinth. They are diverticula of an enlarged unpaired 

 Saccus endolymphaticus, also filled with otoconia, lying dorsally on the spinal cord. 

 These curious chalksacs must be adapted to some special need of the frog. 



Investigation of sixty-five species of Anura, belonging to thirty-five genera, showed 

 that the chalksacs are often absent in Aglossa, Discoglossids and Bufonids, in most 

 Hyhds and Eugystomatids. They are well developed in most Cystignathids and 

 Ranids. 



We found a correlation between the habits of the animal and the chalksacs. These 

 are absent in all purely aquatic Anura, also absent in nearly all tree-living species, 

 whether Hylids, Ranids or Cj'stignathids. Hyla aurea has chalksacs, but it never 

 climbs trees. The Cystignathid Hylodes Schmidti has small chalksacs, but it also 

 climbs trees no more. This points to loss of chalksacs in such Anura that took to 

 cUmbing on trees. Only in one tree-living Hylid, Nototrema, we found well- 

 developed chalksacs. 



Of ground-living Anura, the Bufonids and Engystomatids have none. These 

 forms have very Umited jumping power. When forced to take long jumps, they 

 generally fall on one side or overturn. The only Engystomatid with chalksacs, 

 Rhinoderma, has long legs and jumps remarkably well. AU the Anura that have 



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