PLATE III. 



CORDTLOPHORA LACUSTRIS. 

 FlO. 



1 . Portion of a female colony, magnified ; a, very young gonopliore ; i, gonophore more advanced, 



containing ova, which are embraced by the branches of a ramified spadix, and have their 

 germinal vesicles distinct; c, gonophore still further advanced; the ramifications of the 

 spadix have disappeared, and the segmentation of the vitelius has been completed in the 

 ova ; d, further stage of development, in which the ova have become planulae, and are 

 ready to escape from the gonophore ; e, the gonophore has become ruptured at the 

 summit, and the ciliated planulae are escaping into the surrounding water. 



2. A colony of CordyJopliora lacustris, of the natural size, attached to the under surface of a 



piece of floating tiniijer. 



3. A male gonophore, the spermatic mass embraced by the ramifications of the spadix. 



4. The distal portion of a male gonophore still more magnified : a, external chitinous in- 



vestment, showing layers of deposition; 3, ectotheca ; c, endotheca; d, ramified spadix 



embracing the spermatic mass. 

 .5. Planula much magnified, in two different states of contraction. Its interior is occupied by a 



large cavity, and an ectoderm and endoderm are distinctly visible in its walls. 

 G. The planula after it has lost its cilia and has become fixed. 



7. Further stage of development, in which the distinction between stem and hydranth has 



become apparent, and a verticil of four tentacles has begun to be developed from the 

 hydranth, while the stem has excreted a delicate chitinous perisarc. 



8. The young Cordylophorn still further developed ; the tentacles are still in a single verticil, but 



have increased in length, and the hypostome has become prominent. 



9. Mature s|)ermatozoa ; in the group to the left the heads are still enclosed in the gene- 



rating cell. 



