May 12, 1905.] 



SCIENCE. 



755 



behave in exactly the same manner, whether 

 or not the myodome is present. The prootics 

 meet at the median line above the parasphen- 

 oid and form the floor of the brain cavity or 

 myodome, as the case may be, or they end at 

 the outer edges of the parasphenoid, the latter 

 forming the floor. Perhaps, when the myo- 

 dome is present the prootics meet in fewer 

 cases than when it is not, but both conditions 

 of the prootics are common with both condi- 

 tions of the myodome. (2) In some forms 

 when no myodome appears in the dried skele- 

 ton, if a fresh or alcoholic specimen be exam- 

 ined, a sheet of connective tissue may be 

 found separating the eye muscles from the 

 brain cavity. This tissue is attached to the 

 prootics exactly as the bony shelf is, and pos- 

 sibly the ossification of the shelf takes place 

 in it. 



If this be so it explains why the myodome 

 is of no more value in classification than it 

 is, as there would be little difference between 

 a connective tissue septum and the same tissue 

 replaced by ossification. How great a pro- 

 portion of the forms having no myodome have 

 the connective tissue septum I do not know. 



Looking at the matter in this light there 

 seems little difficulty in my mind in deciding 

 whether Clupea has a myodome. Any cavity 

 between the prootic shelf and the lower sym- 

 physis of the prootics, or between the shelf 

 and the parasphenoid, as the case may be, 

 should be regarded as a myodome. I do not 

 see the application of the fact that the para- 

 sphenoid is open below in Clupea. It is but a 

 difference in degree between the forms where 

 the myodome is open only posteriorly and 

 where it is entirely open below. There are 

 forms with the condition of the opening in- 

 termediate between these two extremes. Of 

 course, the fact that the myodome is open 

 below leaves only a single cranial base inter- 

 preted literally, but it could not be considered 

 under the head of ' basis cranii single,' as it is 

 the primary floor that is missing. 



In examining a large number of fish speci- 

 mens with these problems in view I also had 

 for consideration two other problems in con- 

 nection with the myodome, but unrelated to 

 the above. 



Vrolik* states that the prootic is not pierced 

 by the facial and trigeminus nerves when the 

 myodome is absent, in the forms he has in- 

 vestigated (Gadus, Silurus and Lophius). 1 

 can add my testimony as to the correctness of 

 these conclusions so far as the forms quoted 

 are concerned, but in the following forms, 

 which have no myodome, the prootics are 

 pierced by one or both the fifth and seventh 

 nerves: Tetraodon, Chilomycterus, Lycodes, 

 Dormitator, Opsanus, Brosrne, and perhaps 

 all of the family Blenniidse (six genera were 

 examined). 



On the other hand, I know of no form hav- 

 ing the rnyodome well developed, which has 

 the prootics unpierced. 



The second point I would touch upon is 

 that the dichost (= basisphenoid of Huxley) 

 is always absent when the myodome is. I 

 know of no case where it is at all ossified when 

 the myodome is absent, though there is often 

 a connective tissue septum in this region con- 

 tinued forward as the interocular septum. 



Nearly always the dichost is connected with 

 the edge of the prootic shelf, or roof of the 

 myodome, but that the shelf is not necessary 

 to it is shown by Esox, where it is attached 

 to the parasphenoid at its lower end and is 

 free above. In this case the prootic shelf 

 does not extend very far forward. This prob- 

 lem should be examined in connection with 

 the coimective tissue myodome septum as its 

 ossification is probably of the same sort. 



Edwin Chapin Stauks. 



Rtaxford University, 

 January 19, 1905. 



BOTANICAL NOTES. 



LIFE HISTORY OF THE PINES. 



Last October Professor Dr. Margaret C. 

 Ferguson, of Wellesley College, published in 

 the ' Proceedings of the Washington Academy 

 of Sciences' (Vol. VI., pp. 1-202) an impor- 

 tant paper entitled ' Contributions to the 

 Knowledge of the Life History of Pinus, with 

 Special Eeference to Spermogenesis, the De- 

 velopment of the Gametophytes and Fertiliza- 



* Vrolik, ' Studien iiber die Verknooherung u. 

 d. knochen des Schadels d. Teleostei,' Niederland. 

 Arch. f. Zool., Bd. 1., 1873. 



