VARIATION IN ECHINOID PLUTEI 
675 
Series VIII. 
No arms. Rods passing around the body (fig. 20) , 1 per cent. 
One right anal arm, 4 per cent. 
One left anal arm, 3 per cent. 
Multiple skeletal rods right anal (type, fig. 14), 2 per cent. 
Multiple skeletal rods left anal, 3 per cent. 
Multiple right anal arm, 2 per cent. 
Multiple left anal arm, 2 per cent. 
No oral arms, 6 per cent. 
One right oral arm, 2 per cent. 
One left oral arm, 1 per cent. 
Series IX. 
Median anal arm with multiple rods (type, fig. 6), 2 rods, 4 
per cent, 3 rods 3 per cent. » 
No right anal arm, 5 per cent. 
No left anal arm, 4 per cent. 
Multiple right anal rods (type, fig. 14), 3 per cent. 
Multiple left anal rods (type, fig. 14), 2 per cent. 
Slightly cleft anal ridge, 1 per cent. 
No right oral arm, corresponding left with 2 bars, 2 per cent. 
No left oral arm, corresponding right with 2 bars, 2 per cent. 
Pre-oral region slightly cleft, 1 per cent. 
Pre-oral region uncleft, 1 per cent. 
2. POTENTIAL EGG VARIATIONS 
The results noted in the preceding section indicated the pos- 
sible existence of definite type or line variations. Further in- 
formation on this point seemed desirable and I, therefore, under- 
took a very simple set of experiments. 
Experiment 1. Five females A, B, C, D, and E were selected 
and the eggs of each placed in a separate aquarium. All of these 
were fertilized with sperm from a single male, F. The resulting 
embryos then were AF, BF, CF, DF and EF. Temperature at 
fertiUzation 27° C. During development 27°-28°. 
