210 KINGSLEY AND CONN 



the blastoderm was not seen, the writer feels confident that the posterior end of the alimentary 

 tract arises in the normal way by an invagination of the epiblast to form the proctodeum 

 (fig. 41) and that the division between the two portion breaks down, the result being as 

 shown in figures 44 and 53. Ryder seems to regard this proctodeum as the neurenteric ca- 

 nal. The steps between these two figures were all seen, but the formation of the anterior end 

 of the canal was not witnessed. There are many points of the alimentary tract upon 

 which additional information is needed : the manner of the formation of the mouth, the 

 connection, if any exists, between the yolk sac and the stomach or intestine, and the rela- 

 tions of what is here called the hypoblast of the yolk sac to that of the digestive portion. 

 There are many points in connection with this latter which are absolutely unintelligible 

 to me no matter how looked upon. In fig. 33 this layer is represented as extending beneath 

 the embryo and nowhere united with the alimentary canal and together with another layer 

 starting off on its course around the yolk. Now if this be the hypoblast from which the 

 digestive tract arises, some connection would be expected between them though none has 

 been found. 



The fins which are first seen in an egg about as far advanced as fig. 51, arise in the cun- 

 ner as a simple outgrowth and not as a continuous lateral fold, as is found in many forms. 

 The first skeletal elements appear as a small body at the base of the fin parallel to the 

 body axis and it is not until considerable later that radial portions appear. This basal 

 skeleton instead of appearing as a pair of rods as described by Ryder was rather a broad 

 plate with a central opening, as if his rods had united at their extremities. The same 

 feature was seen in Lophius. 



The remaining features of the development so far as I have clearly made them out can 

 be seen from the plates, and my knowledge is too deficient to say more concerning them 

 than will appear in the explanation of the figures. In about two days from impregna- 

 tion, the fish hatches with a large yolk sac, which in four days more has almost entirely 

 disappeared as shown in fig. 53. The time of hatching I cannot exactly state, in fact 

 it varies considerably with the temperature. Eggs which were impregnated Friday 

 morning at ten o'clock were found hatched Sunday at eleven A. m. (How much before that 

 hour the actual hatching took place I cannot say). The act of hatching was often wit- 

 nessed. The membrane of the eg_>;, yielding to some violent struggles of the embryo 

 bursts open and the young fish emerges usually head first. At the time of hatching the 

 young fish is about a tenth of an inch in length and very slender in proportion. 



