PHELPS ON THE ADHESIVE ORGAN OF AMI A CALVA. 137 



Sumiuary: (1.) The nests of Amia are built by the male fish a con- 

 siderable time in advance of spawning. 



(2.) They are made by biting and tearing away the aquatic plants or 

 other materials on the bottom, so as to form a concavity, the bottom 

 of which is composed of fibrous roots, gravel, or water-soaked cat-tail 

 leaves or other parts of plants. 



(3.) The frequency of the nests depends on the area of available bot- 

 tom, as compared to the number of spawning fish, and varies within wide 

 limits. 



(4.) The spawning occupies several hours and consists of short periods 

 of actual egg laying, alternating Avith longer periods of circling by the 

 male. 



(5.) The same nest may be used by two fish in succession and may 

 contain consequently eggs in widely ditferent stages of development. 



(6.) Nests may be very conspicuous or inconspicuous. 



Zoological Laboratory, University of Michigan, March, 1899. 



THE ORIGIN AND DEVELOPMENT OF THE ADHESIVE ORGAN 



OF AMIA CALVA. 



BY JESSIE PHELPS, YPSILANTI. 



LAb.stract.] 



The adhesive organs of Amia and Lepidosteus and the probable 

 homologous fundaments from which the barbels arise in Acipenser have 

 been described by Dean ('96), Balfour ('81), and V. Kupffer ('91), re- 

 spectively as of ectodermal origin. Certain sections of Amia embryos 

 which Professor Reighard obtained in 1895, led him to suspect that the 

 organ in this form was of entodermal origin. At his suggestion I have 

 collected evidence which entirely justifies this suspicion and which is 

 presented in what follows: 



The adhesive organ of Amia is a larval organ which is functional 

 for only a few days immediately after hatching. At this time the organ 

 consists of a pair of semi-circular or U-shaped ridges, which are so placed 

 on the end of the snout as to form an incomplete ring. Each of these 

 ridges consists of from six to eight cups which open to the surface. 

 The cells of these cups secrete a mucus by which the young animal at- 

 taches itself to the water weeds. As far as the general appearance and 

 structure is concerned one might easily conclude that the organ is 

 ectodermal for it is embedded in the surface ectoblast and shows no 

 connection whatever with the entoblast. But by tracing the history 

 of the cells whicli constitute the organ, they are found to take their 

 origin from among the entodermal cells of the foregut some time before 

 the mouth is formed. At this early period, while the embryo still lies 

 flat upon the yolk, a broad and high dorsally directed enlargement of 

 the anterior extremity of the foregut causes a slight elevation on the 

 exterior immediately in front of the tip of the fore brain. The elevation 

 is crescent shaped and lies with its horns pointing posteriorly. This 

 enlargement or diverticulum of the foregut is the fundament of the 



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