Coalescence and Regeneration m Sponges 255 



larvae did not metamorphose in my experiments but experience 

 with the regenerative tissue suggests that such masses would 

 metamorphose if certain mechanical difficulties due to the great 

 size of the mass were removed. Possibly this might be accom- 

 plished by cutting a flattened sheet composed of some hundred 

 larvae (such as I have produced) into pieces and inducing the 

 pieces to metamorphose separately. 



I may now describe some of the details in this process of larva- 

 fusion. In a species of Lissodendoryx used the larva is of the 

 following character. It has the usual ovoidal shape with a 

 posterior protuberant non-ciliated pole. The anterior pole is 

 somewhat truncated and is sparsely ciliated. The rest of the 

 body bears the usual thick covering of cilia. As seen with reflected 

 light the bulk of the body is dead white, the posterior pole deep 

 blue, and the anterior pole bluish. This coloration is not abso- 

 lutely fixed for the species, but the larvae used in my coalescence 

 experiments were all of this character. Within twenty-four hours 

 after liberation the ciliated larvae are creeping (remaining in con- 

 tact with the bottom as they swim) over the bottom of the dish. 

 Some are now put in deep round watch glasses and with pipette 

 and needle coaxed together into a clump. Fusion soon begins 

 and on the next day plenty of composite larvae are present. The 

 larvae fuse endwise, for the most part in pairs. The compound 

 larva so produced owing to its weight has a very feeble locomotor^ 

 power. Using pairs that are nearly motionless, larvae may be 

 brought together (coaxed with needle) and arranged in a desired 

 position on a cover glass for instance. In successful cases fusion 

 results before the separate masses move apart. In this way, 

 selecting an instance, I have added to one arm of a quadruple 

 mass a pair of larvae, and to the opposite arm two pairs (Fig. 4). 



For the purpose of bringing about the fusion of many larvae the 

 following simple method is convenient. Suppose that we have 

 the larvae in a paraffine-coated dish, and they are in a late "creep- 

 ing" stage. Small excavations, 2-3 mm. deep and 4-5 mm. wide, 

 are now made in the paraffine, and with the pipette the larvae 

 are driven into the holes. They lie here in numbers up to and 

 over one hundred, crowded together and heaped upon one another. 



