54 PHYSIOLOGICAL SERIES. 



B. 35. A Trunk-fish (Ostracion quadricornis) . The greater part 

 of its body is protected by hexagonal bony plates that 

 increase in size by additions to their margins. 



B. 36. Separated bones of the carapace and plastron of a Tortoise 

 (Damonia reevesii). The bones are mostly of dermal origin, 

 and are suturally attached to one another. Growth is 

 effected at the sutural margins. 



B. 37. Cranium from a child aged about 9 years. It is com- 

 posed of separate bones united suturally. Increase in size 

 is effected by additions to their edges, so that the capacity 

 of the skull may keep pace with the growth of the brain. 

 The adult size of the cavity in the frontal region is attained 

 in the second year, the posterior region at a somewhat later 

 period. The position of obliterated sutures are indicated 

 by blue dots. 



Merkel, Beitr. z. Anat. u. Embryol. als Festgabe zttm 

 Henle, 1882, p. 164. 



Joints that by allowing motion, diminish the risk of fracture. 



PLANTS. 



B. 38. A multinucleate calcareous Alga (Ci/mopolia barbata), with 

 a drawing of its structure. Each branch of the thallus 

 consists of a central tube of cellulose lined by chlorophyll- 

 containing protoplasm. It is slightly constricted at short 

 intervals. The constricted part (node) is flexible. The 

 internodes bear whorls of lateral branchlets, those at the 

 proximal end being short, but increasing in length to the 

 distal end. Between the branchlets carbonate of lime is 

 deposited, rendering the internode rigid. The flexibility 

 at the node greatly dimishes the risk of fracture. This 

 plant is found on the shores of the Tropical Atlantic. 

 PI. IX. fig. 1. Presented l>y (jr. R. M. Murray, Esq. 



Cramer Ueber die verticillirten Siphonen (Neomeris 

 und Cymopolia). 



B. 39. A similar specimen and drawing of another calcareous 

 multinucleate Alga (JHalimeda tuna). The fan-shaped 



