140 PROF. W. M. SMALLWOOD ON HYDROIDS [Jan. 18, 



The genital opening is lateral and about one-third of the 

 distance from the rhinophores to the branchiae. It is noticeable 

 as a slight prominence, which is blue in colour. The oviduct is 

 protruded during oviposition and has the pale blue ground-colour. 

 The deposition of the eggs does not seem to occur at any set time 

 during the year. Mr. Mowbray has found eggs during every 

 month of the year, and I secured a large quantity of them during 

 January, 1909. The eggs are laid at any time during the day and 

 often during the night. The external orifice of the oviduct is 

 widely distended, a centimetre or more, and one can see the eggs 

 within this opening for some distance, about 5 mm. The egg- 

 mass (text-fig. 8) is in the form of a long, thick ribbon, often 

 150 mm. long and 15 mm. wide. When free from the animal, 

 this ribbon tends to coil up, and it firmly adheres to the side of 

 the aquarium by one of its edges. Two animals were timed 

 during a part of the act of deposition, and from this as a basis I 

 should estimate that the complete process would take three hours. 



Text-fig. 8. 



Egg-mass of Chromodoris zebra Heilprin. 

 Seen obliquely. £ natural size. 



An hour after the animal ceased laying, some of the eggs, but not 

 all of them, showed two polar bodies. The eggs are laid in the 

 jelly as a continuous string, which takes the form of a somewhat 

 flattened spiral, so that when the broad face of the ribbon is 

 viewed the string usually looks as though regularly folded back 

 and forth across the ribbon. There are about one hundred eggs 

 in a complete turn of the spiral, although this number is not 

 constant. As there are from eighty to one hundred complete turns 

 of the spiral, this would give from eight to ten thousand eggs to 

 a single laying. It would be interesting to know how often each 

 year they are capable of depositing such large numbers of eggs, 

 but it is doubtful if this can be determined, as they are not hardy, 

 soon dying even when placed in running water. It is probable 

 that they come from the deeper water only to spawn, spending 

 the rest of their time at some distance from shore. The egg 

 are of a reddish -brown colour and develop slowly, as is shown 

 by the fact that four and one-half hours after deposition they are 

 still in the one-cell stage. 



In the first lot of Chromodoris zebra collected there were over 

 thirty specimens. The variation in colour was marked ; one 

 specimen of especial interest escaped my attention for a couple of 

 days. This individual on close inspection proved to be a kind of 

 albino. In size, shape, and general habits, it was undoubtedly 



