470 REPORT — 1895. 



closed round so as to nip off the dorsal and ventral vessels entirely from 

 the hypoblast, this brown body is no longer to be seen ; but floating in the 

 liquid of both dorsal and ventral vessels, and also in the vessels of the 

 tentacles, are pale pink-coloured corpuscles, which in sections are seen to 

 have the appearance of broken-off bits of the dark body present in the 

 earlier stage, and containing for the most part each more than one 

 nucleus. There seems to me to be very little doubt that by the further 

 breaking up of such multinucleate corpuscles the blood-corpuscles of the 

 adult (which were described by Benham at the meeting of the British 

 Association last year) would be formed. I was unfortunately not able to 

 obtain later larval stages and to observe this breaking up going on. But 

 I think my sections of what stages I have justify me in concluding that 

 the peculiar dark body of the middle region of the larva is a corpuscle- 

 forming organ. I do not, however, wish to maintain that all the cor- 

 puscles of the adult are formed from this larval organ ; on the contrary, 

 to judge by sections of the adult, which Dr. Bles kindly lent me to look 

 through whilst I was at Plymouth, I think this is at least a .special blood- 

 forming region in the dorsal vessel of the adult ; but, without having 

 intermediate stages, and a complete series of sections of the adult, I 

 cannot say whether this region corresponds to that in which the larval 

 organ lies. I should like to point out the resemblance which this pro- 

 visional larval organ bears, both in structure and position, to what I have 

 called the ' vascular ridge ' in part of the dorsal vessel of Ilekatero- 

 branchus (' Q.J. M.S.,' xxxi. pp. 183, 184, pi. xxii. fig. 6). Like other 

 members of the family Spionida>, Ilekaferobrcmchus has no corpuscles 

 in its blood, and the presence of an organ in the dorsal vessel so closely 

 resembling the one in the dorsal vessel of the larval Magelona suggests, 

 in the light of the facts I have stated above, either that it at one time 

 did have blood-corpuscles formed by a special organ, now persisting only as 

 a vestigial rudiment, or that an organ once having some other significance 

 in both animals has acquired a new significance in the one {Magelona). 



II. On the Kervoiis System of the Embryonic Lobster. 

 By Edgar J. Allen, B.Sc 



Whilst occupying a table at the Marine Biological Association's 

 Laboratory during June and July 189-1 I was enabled to continue my 

 observations on the nervous system of the embryonic lobster. The 

 observations were carried on, as before, with the aid of methylen-blue. 



Additional elements connecting the various ganglia of the thorax 

 with the brain were observed, and their course followed. In the nine 

 ganglia of which the thoracic nerve-chain is really composed, such 

 elements have now been demonstrated in the second (with branches to 

 first and third), the fifth (with branches to fourth and sixth), the eighth 

 (with branches to seventh and ninth), and in the eleventh (with branches 

 to tenth and first abdominal). In this way all the eleven ganglia of the 

 thorax, together with the first abdominal ganglion, are put into direct 

 communication with the brain by means of the four elements whose cells 

 lie in the second, fifth, eighth, and eleventh ganglia. 



Of elements belonging to new types which were observed the most 

 interesting were those motor elements which, taking origin in a single 

 cell, gave rise to two or more branches, which passed out of the central 

 nervous system by the nerve-roots of different ganglia. For example, a 



