464 Gobioidei, Discocephali, and Taeniosomi 



I thought I would try to find it also, and to this end sallied 

 out one morning, armed with a spade, and commenced pros- 

 pecting in a marsh at Berkeley, not far from the State Univer- 

 sity. For a long time I was unsuccessful, as I did not know by 

 what outward signs their habitations could be distinguished, 

 and the extent of mud-bank left bare by the retreating tide 

 was, as compared with my powers of delving, practically limit- 

 less. 



"At last, toward evening, while digging in the bend of a 

 small creek, in a stratum of soft, bluish mud, and at a depth of 

 about a foot below a small puddle, I found five small fishes, 

 which at first I believed to belong to an undescribed species, 

 so little did they resemble the typical G. mirabilis, but which 

 proved, upon a closer examination, to be the young of that 

 species. There was the depressed, broad head, the funnel- 

 shaped ventral ' disk ' formed by the union of the two ventral 

 fins, and the compressed tail of the long-jawed goby, but where 

 were the long jaws? The jaws were, of course, in their usual 

 place, but their prolongations had only just begun to grow along 

 the sides of the head, and were not noticeable unless looked for. 

 A comparison of the various specimens proved conclusively 

 that the strange-looking appendage is developed during the 

 growth of the fish, as will be seen by the following measure- 

 ments of four individuals: 



"In the smallest specimen the maxillary expansion extends 

 beyond the orbit for a distance about equal to that which inter- 

 venes between the anterior margin of the orbit and the tip of 

 the snout; in No. 2 it reaches to the posterior margin of the 

 preoperculum ; in No. 3 it ends level with the gill-opening; 

 while in the largest individual it passes the origin of the pectoral 

 and ventral fins. 



"What can be the use of this long fold of skin and cartilage, 

 which is not attached to the head except where it joins the 

 mouth, and which, from its gradual development and ultimate 

 large dimensions, must certainly serve some useful purpose? 



"Do not understand that I mean that every part of a crea- 

 ture is of use to it in its present mode of life, for, as all natural- 

 ists know, there are in structural anatomy, just as in social 

 life, cases of survival; remains of organs which were at some 



