Normal Plates of the Development of Necturus maculosus. c 



Fig. 30. (X 5-) 



Side view of einhryo 40 days 20 hrs. old, length 18 mm, 44—46 myotomes. The outline of the 

 body shows a marked ventral curvature of the trunk, less pronounced neck bend, and further increase in 

 the dorso-ventral width of the tail. The eye is very prominent owing to the pigment in the retina. Ear 

 not visible externally. Nasal openings very small. The mandibular arches have coalesced. The boundaries 

 of the other arches are no longer discernible. Gill filaments well developed. Anterior limbs about i mm 

 long project dorso-posteriorly. The yolk is elongated oval. Abdominal vein and branchial blood vessels 

 prominent. Pigment present in dorsal portion of head, also along dorsal and lateral portions of trunk and 

 tail. The yolk is unpigmented excepting along dorsal margin. 



Fig- 31. (X 5.) 



Side view of larva 49 days old, lergth 21 mm. General outline of body decidedly different. Head 

 bend obliterated, slight upward curve in trunk. Tail broader. Eye more deeply pigmented. Gill bars very 

 long, extending to level of end of anterior limb. From three to five lateral filaments on each gill bar. 

 Anterior limbs project postero-ventrally ; three digits formed. Posterior limbs directed caudad ; no trace of 

 digits. Yolk much elongated. Network of capillaries denser. Large lateral arteries, at level of upper 

 margin of yolk, very prominent. Well defined longitudinal bands of pigment. 



Fig: 32. (X 5.) 



Side view of larva 61 days old, length 25 mm. General outline of body shows less dorsal curvature 

 of trunk. Tail much longer in proportion to length of trunk and much broader dorso-ventrally. Gill bars 

 longer, each posessing six to eight lateral filaments. Anterior and posterior limbs directed postero-ventrally. 

 Anterior 3 mm long, posterior 2 mm long. Each limb shows four digits. The distribution of pigment is 

 essentially similar to that observed in the 21 mm larva, the bands however are more sharply defined. 

 Chromatophores in the gill bars and limbs and beginning to extend over the dorsal surface of the yolk. 



Fig. 33. (X 5.) 



Side view of larva 70 days 4 hrs. old, length 28 mm. The general outline of the body is slenderer 

 than at any time preceding. The rapid absorption of the yolk has brought its ventral surface nearly to the 

 level of the ventral surfaces of the head and tail. The gill bars curve dorsally and possess fi;om ten to 

 twelve pairs of lateral filaments. The tail is somewhat constricted at the level of the posterior limbs. The 

 limbs and digits are better developed and are now used in locomotion. Pigmentation is denser than in 

 25 mm larva, but same general arrangement of bands prevails. 



Fig. 34. (X 50 



Side view of larva 97 days old, length 34 mm. In general outline the larva begins to resemble the 

 adult. The yolk is well absorbed. The tail is very broad and now used as a powerful caudal fin in 

 swimming. The gill bars project dorsally and have a large number of filaments. The legs project far 

 below the ventral surface of the body. In color the same general pattern prevails as in the 28 mm larva. 



