302 



TYPES OF LARV.E. 



ECHINODEEMATA. The Auriciilaria (fig. 223 A), the Bipinnaria (fig. 223 B), and the 

 Pluteus (fig. 224), and the transversely-ringed larvse of Crinoidea (vol. i. fig. 268). The 

 three first of which can be reduced to a common type (fig. 231 c). 



ENTEROPNEUSTA. Toruaria (fig. 229). 



UROCHORDA (TDNICATA). The tadpole- like larva (vol. n. fig. 8). 



GANOIDEI. A larva with a disc with adhesive papilla in front of the mouth (vol. IT. 



fig. 67). 



ANUROUS AMPHIBIA. The tadpole (vol. n. fig. 80). 



Of the larval forms included in the above list a certain number 

 are probably without affinities outside the group to which they 

 belong. This is the case with the larvse of the Myriapoda, the 

 Crustacean larvae, and with the larval forms of the Chordata. I 

 shall leave these forms out of consideration. 



en 



en 



c. 



FlG. 215. TWO FREE STAGES IN THE DEVELOPMENT OF SYCANDRA RAPHANU8. 



(After Schultze.) 



A. Amphiblastula stage. 



B. Stage after the ciliated cells have commenced to he invaginated. 



c.s. segmentation cavity; ec. granular epiblast cells; en. ciliated hypoblast cells. 



There are, again, some larval forms which may possibly turn out 

 hereafter to be of importance, but from which, in the present state of 

 our knowledge, we cannot draw any conclusions. The infusoriform 

 larva of the Dicyemidse, and the Cercaria of the Trematodes, are such 

 forms. 



Excluding these and certain other forms, we have finally left for 

 consideration the larvce of the Coelenterata, the Turbellaria, the 

 Rotifera, the Nemertea, the Mollusca, the Polyzoa, the Brachiopoda, 

 the Chsetopoda, the Gephyrea, the Echinodermata, and the Entero- 

 pneusta. 



The larvse of these forms can be divided into two groups. The 

 one group contains the larva of the Coelenterata or Planula, the other 

 group the larvse of all the other forms. 



