M. Sars on the Development of the Annelides. 187 
his eyes. I therefore refer to his observations, as probably the 
further development of our young Polynoé takes place in a coim- 
cident manner. 
The results of the above observations are briefly as follows :— 
1. Polynoé cirrata propagates in the months of April and 
March by ova which are secreted from particular apertures on 
the dorsal side in masses connected together by mucous fila- 
ments ; they collect on the back and under the branchie of the 
mother, where they remain during their further development 
and until the exit of the young. The branchiz have here there- 
fore a similar function as in the freshwater Mollusca (Unio, Ana- 
donta), that of protecting the brood. 
2. The young when they leave the egg have a very different 
form from that of the mother and a very imperfect structure. 
_ They are short, oval,cylindrical, unarticulated, and so to say, little 
more than mere head, for this occupies more than half of the en- 
tire body, and has two very distinct eyes (the full-grown animal 
has, as is well known, four). The mouth is a horizontal fissure 
on the ventral side of the body, and the anus is situated at its 
posterior extremity. With the exception of a circle of cilia, which 
surround horizontally the centre of the body and effect locomo- 
tion, there exist no other external members, no tentacula or an- 
tennze, no feet with their appendages of cirrhi and bristles, and no 
branchiz. All these organs must therefore be developed sub- 
sequently, when the true body (abdomen) has grown and become 
divided into articulations (as the observations of Lovén show), as 
well as the two eyes, which are still deficient, while the cilia, as 
transitory, disappear. In short, we have here all the criteria of a 
metamorphosis,—different external form, parts which disappear 
entirely, and numerous organs which are subsequently added. 
It is therefore certain that many Annelides undergo a very 
considerable metamorphosis. In this respect they are related to 
the other Articulata, and indeed most to the Myriapoda, whose 
young, according to the observations of Waga and Newport, leave 
the egg in a very imperfect state and without any articulated 
members. 
As connected with this subject, I must mention the mucous 
globules which are likewise met with in the months of: Fe- 
bruary and March on our coast, adhering at the depth of some 
feet to Zostera marina and Fucus vesiculosus. These globules 
(fig. 20) are about an inch in diameter, of a beautiful grass-green 
colour, and consist of an immense number of eggs (bb) enveloped 
in a tenacious mucus which is rolled irregularly like a riband 
into a knot, the whole of which is coated with a slimy envelope. 
The eggs are globular, filled with lmpid chorion, somewhat al- 
bumen, and grass-green yolk, which I observed in all the various 
